diff --git a/content/base/src/nsMappedAttributes.cpp b/content/base/src/nsMappedAttributes.cpp
index a58e845cf9b..c12243fda12 100644
--- a/content/base/src/nsMappedAttributes.cpp
+++ b/content/base/src/nsMappedAttributes.cpp
@@ -195,17 +195,16 @@ nsMappedAttributes::SetStyleSheet(nsHTMLStyleSheet* aSheet)
   mSheet = aSheet;  // not ref counted
 }
 
-NS_IMETHODIMP
+/* virtual */ void
 nsMappedAttributes::MapRuleInfoInto(nsRuleData* aRuleData)
 {
   if (mRuleMapper) {
     (*mRuleMapper)(this, aRuleData);
   }
-  return NS_OK;
 }
 
 #ifdef DEBUG
-NS_IMETHODIMP
+/* virtual */ void
 nsMappedAttributes::List(FILE* out, PRInt32 aIndent) const
 {
   nsAutoString buffer;
@@ -228,8 +227,6 @@ nsMappedAttributes::List(FILE* out, PRInt32 aIndent) const
     fputs(NS_LossyConvertUTF16toASCII(buffer).get(), out);
     fputs("\n", out);
   }
-
-  return NS_OK;
 }
 #endif
 
diff --git a/content/base/src/nsMappedAttributes.h b/content/base/src/nsMappedAttributes.h
index cb196b4efaf..7367779cd18 100644
--- a/content/base/src/nsMappedAttributes.h
+++ b/content/base/src/nsMappedAttributes.h
@@ -103,9 +103,9 @@ public:
   
 
   // nsIStyleRule 
-  NS_IMETHOD MapRuleInfoInto(nsRuleData* aRuleData);
+  virtual void MapRuleInfoInto(nsRuleData* aRuleData);
 #ifdef DEBUG
-  NS_METHOD List(FILE* out = stdout, PRInt32 aIndent = 0) const;
+  virtual void List(FILE* out = stdout, PRInt32 aIndent = 0) const;
 #endif
 
 private:
diff --git a/content/html/content/src/nsHTMLBodyElement.cpp b/content/html/content/src/nsHTMLBodyElement.cpp
index 38b42114721..9d18b1b1c32 100644
--- a/content/html/content/src/nsHTMLBodyElement.cpp
+++ b/content/html/content/src/nsHTMLBodyElement.cpp
@@ -69,9 +69,9 @@ public:
   NS_DECL_ISUPPORTS
 
   // nsIStyleRule interface
-  NS_IMETHOD MapRuleInfoInto(nsRuleData* aRuleData);
+  virtual void MapRuleInfoInto(nsRuleData* aRuleData);
 #ifdef DEBUG
-  NS_IMETHOD List(FILE* out = stdout, PRInt32 aIndent = 0) const;
+  virtual void List(FILE* out = stdout, PRInt32 aIndent = 0) const;
 #endif
 
   nsHTMLBodyElement*  mPart;  // not ref-counted, cleared by content 
@@ -132,11 +132,11 @@ BodyRule::~BodyRule()
 
 NS_IMPL_ISUPPORTS1(BodyRule, nsIStyleRule)
 
-NS_IMETHODIMP
+/* virtual */ void
 BodyRule::MapRuleInfoInto(nsRuleData* aData)
 {
   if (!aData || !(aData->mSIDs & NS_STYLE_INHERIT_BIT(Margin)) || !aData->mMarginData || !mPart)
-    return NS_OK; // We only care about margins.
+    return; // We only care about margins.
 
   PRInt32 bodyMarginWidth  = -1;
   PRInt32 bodyMarginHeight = -1;
@@ -261,14 +261,12 @@ BodyRule::MapRuleInfoInto(nsRuleData* aData)
       }
     }
   }
-  return NS_OK;
 }
 
 #ifdef DEBUG
-NS_IMETHODIMP
+/* virtual */ void
 BodyRule::List(FILE* out, PRInt32 aIndent) const
 {
-  return NS_OK;
 }
 #endif
 
diff --git a/content/svg/content/src/nsSVGElement.h b/content/svg/content/src/nsSVGElement.h
index ea263cf53df..0d9e768c06d 100644
--- a/content/svg/content/src/nsSVGElement.h
+++ b/content/svg/content/src/nsSVGElement.h
@@ -70,6 +70,7 @@ struct nsSVGEnumMapping;
 class nsSVGViewBox;
 class nsSVGPreserveAspectRatio;
 class nsSVGString;
+struct gfxMatrix;
 
 typedef nsStyledElement nsSVGElementBase;
 
diff --git a/layout/style/nsCSSDataBlock.cpp b/layout/style/nsCSSDataBlock.cpp
index bd64c589302..73907c51e82 100644
--- a/layout/style/nsCSSDataBlock.cpp
+++ b/layout/style/nsCSSDataBlock.cpp
@@ -218,7 +218,7 @@ ShouldStartImageLoads(nsRuleData *aRuleData, nsCSSProperty aProperty)
          nsCSSProps::PropHasFlags(aProperty, CSS_PROPERTY_START_IMAGE_LOADS);
 }
 
-nsresult
+void
 nsCSSCompressedDataBlock::MapRuleInfoInto(nsRuleData *aRuleData) const
 {
     // If we have no data for these structs, then return immediately.
@@ -226,7 +226,7 @@ nsCSSCompressedDataBlock::MapRuleInfoInto(nsRuleData *aRuleData) const
     // have to worry much less (although still some) about the speed of
     // the rest of the function.
     if (!(aRuleData->mSIDs & mStyleBits))
-        return NS_OK;
+        return;
 
     nsIDocument* doc = aRuleData->mPresContext->Document();
 
@@ -358,8 +358,6 @@ nsCSSCompressedDataBlock::MapRuleInfoInto(nsRuleData *aRuleData) const
         }
     }
     NS_ASSERTION(cursor == cursor_end, "inconsistent data");
-
-    return NS_OK;
 }
 
 const void*
diff --git a/layout/style/nsCSSDataBlock.h b/layout/style/nsCSSDataBlock.h
index 35d0af909cc..e65308005bc 100644
--- a/layout/style/nsCSSDataBlock.h
+++ b/layout/style/nsCSSDataBlock.h
@@ -72,7 +72,7 @@ public:
      * Do what |nsIStyleRule::MapRuleInfoInto| needs to do for a style
      * rule using this block for storage.
      */
-    nsresult MapRuleInfoInto(nsRuleData *aRuleData) const;
+    void MapRuleInfoInto(nsRuleData *aRuleData) const;
 
     /**
      * Return the location at which the *value* for the property is
diff --git a/layout/style/nsCSSRule.cpp b/layout/style/nsCSSRule.cpp
index 660daadc47e..bdd36edb5d5 100644
--- a/layout/style/nsCSSRule.cpp
+++ b/layout/style/nsCSSRule.cpp
@@ -89,10 +89,9 @@ nsCSSRule::SetParentRule(nsICSSGroupRule* aRule)
   return NS_OK;
 }
 
-NS_IMETHODIMP
+/* virtual */ void
 nsCSSRule::MapRuleInfoInto(nsRuleData* aRuleData)
 {
   // The nsIStyleRule contract is not appropriate for all CSS rules.
   NS_NOTREACHED("nsCSSRule::MapRuleInfoInto");
-  return NS_OK;
 }
diff --git a/layout/style/nsCSSRule.h b/layout/style/nsCSSRule.h
index c1394a730f1..104f36d1d78 100644
--- a/layout/style/nsCSSRule.h
+++ b/layout/style/nsCSSRule.h
@@ -68,7 +68,7 @@ public:
 
   // nsIStyleRule methods
   // The new mapping function.
-  NS_IMETHOD MapRuleInfoInto(nsRuleData* aRuleData);
+  virtual void MapRuleInfoInto(nsRuleData* aRuleData);
 
 protected:
   nsCSSStyleSheet*    mSheet;
diff --git a/layout/style/nsCSSRules.cpp b/layout/style/nsCSSRules.cpp
index 57abc5237a3..14554f1239e 100644
--- a/layout/style/nsCSSRules.cpp
+++ b/layout/style/nsCSSRules.cpp
@@ -78,12 +78,12 @@ NS_IMETHODIMP _class::GetStyleSheet(nsIStyleSheet*& aSheet) const { return super
 NS_IMETHODIMP _class::SetStyleSheet(nsCSSStyleSheet* aSheet) { return super::SetStyleSheet(aSheet); }  \
 NS_IMETHODIMP _class::SetParentRule(nsICSSGroupRule* aRule) { return super::SetParentRule(aRule); }  \
 nsIDOMCSSRule* _class::GetDOMRuleWeak(nsresult *aResult) { *aResult = NS_OK; return this; }  \
-NS_IMETHODIMP _class::MapRuleInfoInto(nsRuleData* aRuleData) { return NS_OK; } 
+/* virtual */ void _class::MapRuleInfoInto(nsRuleData* aRuleData) { }
 
 #define IMPL_STYLE_RULE_INHERIT2(_class, super) \
 NS_IMETHODIMP _class::GetStyleSheet(nsIStyleSheet*& aSheet) const { return super::GetStyleSheet(aSheet); }  \
 NS_IMETHODIMP _class::SetParentRule(nsICSSGroupRule* aRule) { return super::SetParentRule(aRule); }  \
-NS_IMETHODIMP _class::MapRuleInfoInto(nsRuleData* aRuleData) { return NS_OK; } 
+/* virtual */ void _class::MapRuleInfoInto(nsRuleData* aRuleData) { }
 
 // -------------------------------
 // Style Rule List for group rules
@@ -200,7 +200,7 @@ public:
 
   // nsIStyleRule methods
 #ifdef DEBUG
-  NS_IMETHOD List(FILE* out = stdout, PRInt32 aIndent = 0) const;
+  virtual void List(FILE* out = stdout, PRInt32 aIndent = 0) const;
 #endif
 
   // nsICSSRule methods
@@ -252,7 +252,7 @@ NS_INTERFACE_MAP_END
 IMPL_STYLE_RULE_INHERIT(CSSCharsetRuleImpl, nsCSSRule)
 
 #ifdef DEBUG
-NS_IMETHODIMP
+/* virtual */ void
 CSSCharsetRuleImpl::List(FILE* out, PRInt32 aIndent) const
 {
   // Indent
@@ -261,8 +261,6 @@ CSSCharsetRuleImpl::List(FILE* out, PRInt32 aIndent) const
   fputs("@charset \"", out);
   fputs(NS_LossyConvertUTF16toASCII(mEncoding).get(), out);
   fputs("\"\n", out);
-
-  return NS_OK;
 }
 #endif
 
@@ -376,7 +374,7 @@ public:
 
   // nsIStyleRule methods
 #ifdef DEBUG
-  NS_IMETHOD List(FILE* out = stdout, PRInt32 aIndent = 0) const;
+  virtual void List(FILE* out = stdout, PRInt32 aIndent = 0) const;
 #endif
 
   // nsICSSRule methods
@@ -452,7 +450,7 @@ NS_INTERFACE_MAP_END
 IMPL_STYLE_RULE_INHERIT(CSSImportRuleImpl, nsCSSRule)
 
 #ifdef DEBUG
-NS_IMETHODIMP
+/* virtual */ void
 CSSImportRuleImpl::List(FILE* out, PRInt32 aIndent) const
 {
   // Indent
@@ -466,8 +464,6 @@ CSSImportRuleImpl::List(FILE* out, PRInt32 aIndent) const
   mMedia->GetText(mediaText);
   fputs(NS_LossyConvertUTF16toASCII(mediaText).get(), out);
   fputs("\n", out);
-
-  return NS_OK;
 }
 #endif
 
@@ -700,7 +696,7 @@ nsCSSGroupRule::SetStyleSheet(nsCSSStyleSheet* aSheet)
 }
 
 #ifdef DEBUG
-NS_IMETHODIMP
+/* virtual */ void
 nsCSSGroupRule::List(FILE* out, PRInt32 aIndent) const
 {
   fputs(" {\n", out);
@@ -709,7 +705,6 @@ nsCSSGroupRule::List(FILE* out, PRInt32 aIndent) const
     mRules.ObjectAt(index)->List(out, aIndent + 1);
   }
   fputs("}\n", out);
-  return NS_OK;
 }
 #endif
 
@@ -934,7 +929,7 @@ nsCSSMediaRule::SetStyleSheet(nsCSSStyleSheet* aSheet)
 }
 
 #ifdef DEBUG
-NS_IMETHODIMP
+/* virtual */ void
 nsCSSMediaRule::List(FILE* out, PRInt32 aIndent) const
 {
   for (PRInt32 indent = aIndent; --indent >= 0; ) fputs("  ", out);
@@ -949,7 +944,7 @@ nsCSSMediaRule::List(FILE* out, PRInt32 aIndent) const
     fputs(NS_LossyConvertUTF16toASCII(mediaText).get(), out);
   }
 
-  return nsCSSGroupRule::List(out, aIndent);
+  nsCSSGroupRule::List(out, aIndent);
 }
 #endif
 
@@ -1094,7 +1089,7 @@ NS_INTERFACE_MAP_BEGIN(nsCSSDocumentRule)
 NS_INTERFACE_MAP_END
 
 #ifdef DEBUG
-NS_IMETHODIMP
+/* virtual */ void
 nsCSSDocumentRule::List(FILE* out, PRInt32 aIndent) const
 {
   for (PRInt32 indent = aIndent; --indent >= 0; ) fputs("  ", out);
@@ -1121,7 +1116,7 @@ nsCSSDocumentRule::List(FILE* out, PRInt32 aIndent) const
   str.Cut(str.Length() - 2, 1); // remove last ,
   fputs(str.get(), out);
 
-  return nsCSSGroupRule::List(out, aIndent);
+  nsCSSGroupRule::List(out, aIndent);
 }
 #endif
 
@@ -1276,7 +1271,7 @@ public:
 
   // nsIStyleRule methods
 #ifdef DEBUG
-  NS_IMETHOD List(FILE* out = stdout, PRInt32 aIndent = 0) const;
+  virtual void List(FILE* out = stdout, PRInt32 aIndent = 0) const;
 #endif
 
   // nsICSSRule methods
@@ -1336,7 +1331,7 @@ NS_INTERFACE_MAP_END
 IMPL_STYLE_RULE_INHERIT(CSSNameSpaceRuleImpl, nsCSSRule)
 
 #ifdef DEBUG
-NS_IMETHODIMP
+/* virtual */ void
 CSSNameSpaceRuleImpl::List(FILE* out, PRInt32 aIndent) const
 {
   for (PRInt32 indent = aIndent; --indent >= 0; ) fputs("  ", out);
@@ -1354,7 +1349,6 @@ CSSNameSpaceRuleImpl::List(FILE* out, PRInt32 aIndent) const
   fputs("url(", out);
   fputs(NS_LossyConvertUTF16toASCII(mURLSpec).get(), out);
   fputs(")\n", out);
-  return NS_OK;
 }
 #endif
 
@@ -1825,7 +1819,7 @@ NS_INTERFACE_MAP_END
 IMPL_STYLE_RULE_INHERIT(nsCSSFontFaceRule, nsCSSRule)
 
 #ifdef DEBUG
-NS_IMETHODIMP
+void
 nsCSSFontFaceRule::List(FILE* out, PRInt32 aIndent) const
 {
   nsCString baseInd, descInd;
@@ -1852,7 +1846,6 @@ nsCSSFontFaceRule::List(FILE* out, PRInt32 aIndent) const
               NS_ConvertUTF16toUTF8(descStr).get());
     }
   fprintf(out, "%s}\n", baseInd.get());
-  return NS_OK;
 }
 #endif
 
diff --git a/layout/style/nsCSSRules.h b/layout/style/nsCSSRules.h
index e3eeb2ccf09..82f54fd3631 100644
--- a/layout/style/nsCSSRules.h
+++ b/layout/style/nsCSSRules.h
@@ -60,7 +60,7 @@ class nsMediaList;
 NS_IMETHOD GetStyleSheet(nsIStyleSheet*& aSheet) const; \
 NS_IMETHOD SetStyleSheet(nsCSSStyleSheet* aSheet); \
 NS_IMETHOD SetParentRule(nsICSSGroupRule* aRule); \
-NS_IMETHOD MapRuleInfoInto(nsRuleData* aRuleData);
+virtual void MapRuleInfoInto(nsRuleData* aRuleData);
 
 #define DECL_STYLE_RULE_INHERIT  \
 DECL_STYLE_RULE_INHERIT_NO_DOMRULE \
@@ -80,7 +80,7 @@ protected:
 
   // to help implement nsIStyleRule
 #ifdef DEBUG
-  NS_IMETHOD List(FILE* out = stdout, PRInt32 aIndent = 0) const;
+  virtual void List(FILE* out = stdout, PRInt32 aIndent = 0) const;
 #endif
 
 public:
@@ -124,7 +124,7 @@ public:
 
   // nsIStyleRule methods
 #ifdef DEBUG
-  NS_IMETHOD List(FILE* out = stdout, PRInt32 aIndent = 0) const;
+  virtual void List(FILE* out = stdout, PRInt32 aIndent = 0) const;
 #endif
 
   // nsICSSRule methods
@@ -166,7 +166,7 @@ public:
 
   // nsIStyleRule methods
 #ifdef DEBUG
-  NS_IMETHOD List(FILE* out = stdout, PRInt32 aIndent = 0) const;
+  virtual void List(FILE* out = stdout, PRInt32 aIndent = 0) const;
 #endif
 
   // nsICSSRule methods
@@ -255,7 +255,7 @@ public:
 
   // nsIStyleRule methods
 #ifdef DEBUG
-  NS_IMETHOD List(FILE* out = stdout, PRInt32 aIndent = 0) const;
+  virtual void List(FILE* out = stdout, PRInt32 aIndent = 0) const;
 #endif
 
   // nsICSSRule methods
diff --git a/layout/style/nsCSSStyleRule.cpp b/layout/style/nsCSSStyleRule.cpp
index c73e0245db7..6273184e8b3 100644
--- a/layout/style/nsCSSStyleRule.cpp
+++ b/layout/style/nsCSSStyleRule.cpp
@@ -903,9 +903,9 @@ public:
   NS_DECL_ISUPPORTS
 
   // nsIStyleRule interface
-  NS_IMETHOD MapRuleInfoInto(nsRuleData* aRuleData);
+  virtual void MapRuleInfoInto(nsRuleData* aRuleData);
 #ifdef DEBUG
-  NS_IMETHOD List(FILE* out = stdout, PRInt32 aIndent = 0) const;
+  virtual void List(FILE* out = stdout, PRInt32 aIndent = 0) const;
 #endif
 
 protected:
@@ -927,14 +927,14 @@ CSSImportantRule::~CSSImportantRule(void)
 
 NS_IMPL_ISUPPORTS1(CSSImportantRule, nsIStyleRule)
 
-NS_IMETHODIMP
+/* virtual */ void
 CSSImportantRule::MapRuleInfoInto(nsRuleData* aRuleData)
 {
-  return mImportantBlock->MapRuleInfoInto(aRuleData);
+  mImportantBlock->MapRuleInfoInto(aRuleData);
 }
 
 #ifdef DEBUG
-NS_IMETHODIMP
+/* virtual */ void
 CSSImportantRule::List(FILE* out, PRInt32 aIndent) const
 {
   // Indent
@@ -942,7 +942,6 @@ CSSImportantRule::List(FILE* out, PRInt32 aIndent) const
 
   fprintf(out, "! Important rule block=%p\n",
           static_cast<void*>(mImportantBlock.get()));
-  return NS_OK;
 }
 #endif
 
@@ -1319,10 +1318,10 @@ public:
     DeclarationChanged(PRBool aHandleContainer);
 
   // The new mapping function.
-  NS_IMETHOD MapRuleInfoInto(nsRuleData* aRuleData);
+  virtual void MapRuleInfoInto(nsRuleData* aRuleData);
 
 #ifdef DEBUG
-  NS_IMETHOD List(FILE* out = stdout, PRInt32 aIndent = 0) const;
+  virtual void List(FILE* out = stdout, PRInt32 aIndent = 0) const;
 #endif
 
 private: 
@@ -1550,16 +1549,16 @@ CSSStyleRuleImpl::DeclarationChanged(PRBool aHandleContainer)
   return clone;
 }
 
-NS_IMETHODIMP
+/* virtual */ void
 CSSStyleRuleImpl::MapRuleInfoInto(nsRuleData* aRuleData)
 {
   NS_ABORT_IF_FALSE(mNormalBlock,
                     "somebody forgot to call nsICSSStyleRule::RuleMatched");
-  return mNormalBlock->MapRuleInfoInto(aRuleData);
+  mNormalBlock->MapRuleInfoInto(aRuleData);
 }
 
 #ifdef DEBUG
-NS_IMETHODIMP
+/* virtual */ void
 CSSStyleRuleImpl::List(FILE* out, PRInt32 aIndent) const
 {
   // Indent
@@ -1578,8 +1577,6 @@ CSSStyleRuleImpl::List(FILE* out, PRInt32 aIndent) const
     fputs("{ null declaration }", out);
   }
   fputs("\n", out);
-
-  return NS_OK;
 }
 #endif
 
diff --git a/layout/style/nsHTMLStyleSheet.cpp b/layout/style/nsHTMLStyleSheet.cpp
index e2464436b28..b55aa5d8ab3 100644
--- a/layout/style/nsHTMLStyleSheet.cpp
+++ b/layout/style/nsHTMLStyleSheet.cpp
@@ -76,7 +76,7 @@ using namespace mozilla::dom;
 
 NS_IMPL_ISUPPORTS1(nsHTMLStyleSheet::HTMLColorRule, nsIStyleRule)
 
-NS_IMETHODIMP
+/* virtual */ void
 nsHTMLStyleSheet::HTMLColorRule::MapRuleInfoInto(nsRuleData* aRuleData)
 {
   if (aRuleData->mSIDs & NS_STYLE_INHERIT_BIT(Color)) {
@@ -84,36 +84,32 @@ nsHTMLStyleSheet::HTMLColorRule::MapRuleInfoInto(nsRuleData* aRuleData)
         aRuleData->mPresContext->UseDocumentColors())
       aRuleData->mColorData->mColor.SetColorValue(mColor);
   }
-  return NS_OK;
 }
 
 #ifdef DEBUG
-NS_IMETHODIMP
+/* virtual */ void
 nsHTMLStyleSheet::HTMLColorRule::List(FILE* out, PRInt32 aIndent) const
 {
-  return NS_OK;
 }
 #endif
 
  
 NS_IMPL_ISUPPORTS1(nsHTMLStyleSheet::GenericTableRule, nsIStyleRule)
 
-NS_IMETHODIMP
+/* virtual */ void
 nsHTMLStyleSheet::GenericTableRule::MapRuleInfoInto(nsRuleData* aRuleData)
 {
   // Nothing to do.
-  return NS_OK;
 }
 
 #ifdef DEBUG
-NS_IMETHODIMP
+/* virtual */ void
 nsHTMLStyleSheet::GenericTableRule::List(FILE* out, PRInt32 aIndent) const
 {
-  return NS_OK;
 }
 #endif
 
-NS_IMETHODIMP
+/* virtual */ void
 nsHTMLStyleSheet::TableTHRule::MapRuleInfoInto(nsRuleData* aRuleData)
 {
   if (aRuleData->mSIDs & NS_STYLE_INHERIT_BIT(Text)) {
@@ -123,7 +119,6 @@ nsHTMLStyleSheet::TableTHRule::MapRuleInfoInto(nsRuleData* aRuleData)
                     eCSSUnit_Enumerated);
     }
   }
-  return NS_OK;
 }
 
 // -----------------------------------------------------------
diff --git a/layout/style/nsHTMLStyleSheet.h b/layout/style/nsHTMLStyleSheet.h
index dba8a7ccd16..9a932f2f9f7 100644
--- a/layout/style/nsHTMLStyleSheet.h
+++ b/layout/style/nsHTMLStyleSheet.h
@@ -119,9 +119,9 @@ private:
     NS_DECL_ISUPPORTS
 
     // nsIStyleRule interface
-    NS_IMETHOD MapRuleInfoInto(nsRuleData* aRuleData);
+    virtual void MapRuleInfoInto(nsRuleData* aRuleData);
   #ifdef DEBUG
-    NS_IMETHOD List(FILE* out = stdout, PRInt32 aIndent = 0) const;
+    virtual void List(FILE* out = stdout, PRInt32 aIndent = 0) const;
   #endif
 
     nscolor             mColor;
@@ -137,9 +137,9 @@ private:
     NS_DECL_ISUPPORTS
 
     // nsIStyleRule interface
-    NS_IMETHOD MapRuleInfoInto(nsRuleData* aRuleData);
+    virtual void MapRuleInfoInto(nsRuleData* aRuleData);
   #ifdef DEBUG
-    NS_IMETHOD List(FILE* out = stdout, PRInt32 aIndent = 0) const;
+    virtual void List(FILE* out = stdout, PRInt32 aIndent = 0) const;
   #endif
   };
 
@@ -150,7 +150,7 @@ private:
   public:
     TableTHRule() {}
 
-    NS_IMETHOD MapRuleInfoInto(nsRuleData* aRuleData);
+    virtual void MapRuleInfoInto(nsRuleData* aRuleData);
   };
 
   nsCOMPtr<nsIURI>        mURL;
diff --git a/layout/style/nsICSSGroupRule.h b/layout/style/nsICSSGroupRule.h
index 9cd7422ef66..602b6f8a65b 100644
--- a/layout/style/nsICSSGroupRule.h
+++ b/layout/style/nsICSSGroupRule.h
@@ -46,13 +46,13 @@
 #include "nsICSSRule.h"
 #include "nsCOMArray.h"
 
-class nsIAtom;
 class nsPresContext;
 class nsMediaQueryResultCacheKey;
 
-// IID for the nsICSSGroupRule interface {d0f07b17-e9c7-4a54-aaa4-622425b38d27}
+// IID for the nsICSSGroupRule interface {4d5e7eca-433e-491a-b226-39a200390ea1}
 #define NS_ICSS_GROUP_RULE_IID     \
-{0xd0f07b17, 0xe9c7, 0x4a54, {0xaa, 0xa4, 0x62, 0x24, 0x25, 0xb3, 0x8d, 0x27}}
+{0x4d5e7eca, 0x433e, 0x491a, {0xb2, 0x26, 0x39, 0xa2, 0x00, 0x39, 0x0e, 0xa1}}
+
 
 class nsICSSGroupRule : public nsICSSRule {
 public:
diff --git a/layout/style/nsICSSImportRule.h b/layout/style/nsICSSImportRule.h
index a13070418d1..05c1471bddc 100644
--- a/layout/style/nsICSSImportRule.h
+++ b/layout/style/nsICSSImportRule.h
@@ -41,15 +41,14 @@
 #define nsICSSImportRule_h___
 
 #include "nsICSSRule.h"
-#include "nsString.h"
 
-class nsIAtom;
-class nsIURI;
 class nsMediaList;
+class nsString;
 
-// IID for the nsICSSImportRule interface {b2e65d15-6673-4548-a65a-c45ce87304f2}
+// IID for the nsICSSImportRule interface {1d7a658b-2f7b-423d-a3d9-dd5b553f69a9}
 #define NS_ICSS_IMPORT_RULE_IID     \
-{0xb2e65d15, 0x6673, 0x4548, {0xa6, 0x5a, 0xc4, 0x5c, 0xe8, 0x73, 0x04, 0xf2}}
+{0x1d7a658b, 0x2f7b, 0x423d, {0xa3, 0xd9, 0xdd, 0x5b, 0x55, 0x3f, 0x69, 0xa9}}
+
 
 class nsICSSImportRule : public nsICSSRule {
 public:
diff --git a/layout/style/nsICSSNameSpaceRule.h b/layout/style/nsICSSNameSpaceRule.h
index 5c503cc25fa..98e77ffe2e1 100644
--- a/layout/style/nsICSSNameSpaceRule.h
+++ b/layout/style/nsICSSNameSpaceRule.h
@@ -41,13 +41,13 @@
 #define nsICSSNameSpaceRule_h___
 
 #include "nsICSSRule.h"
-//#include "nsString.h"
 
 class nsIAtom;
 
-// IID for the nsICSSNameSpaceRule interface {c2116a9f-370d-458a-80c1-c6445089a8b7}
+// IID for the nsICSSNameSpaceRule interface {153392d4-90bb-424e-b737-1bf5bc775394}
 #define NS_ICSS_NAMESPACE_RULE_IID     \
-{0xc2116a9f, 0x370d, 0x458a, {0x80, 0xc1, 0xc6, 0x44, 0x50, 0x89, 0xa8, 0xb7}}
+{0x153392d4, 0x90bb, 0x424e, {0xb7, 0x37, 0x1b, 0xf5, 0xbc, 0x77, 0x53, 0x94}}
+
 
 class nsICSSNameSpaceRule : public nsICSSRule {
 public:
diff --git a/layout/style/nsICSSRule.h b/layout/style/nsICSSRule.h
index 28ed016e71e..86b55cef433 100644
--- a/layout/style/nsICSSRule.h
+++ b/layout/style/nsICSSRule.h
@@ -47,10 +47,11 @@ class nsCSSStyleSheet;
 class nsICSSGroupRule;
 class nsAString;
 
-// IID for the nsICSSRule interface {72250d73-dbb2-4409-90fe-e8e0283a2510}
+// IID for the nsICSSRule interface {2a1fef35-eee9-4a5d-bc87-e2228acc926b}
 #define NS_ICSS_RULE_IID     \
-{ 0x72250d73, 0xdbb2, 0x4409, \
- { 0x90, 0xfe, 0xe8, 0xe0, 0x28, 0x3a, 0x25, 0x10 } }
+{ 0x2a1fef35, 0xeee9, 0x4a5d, \
+ { 0xbc, 0x87, 0xe2, 0x22, 0x8a, 0xcc, 0x92, 0x6b } }
+
 
 // inheriting from nsIStyleRule is only for style rules, not other rule types
 class nsICSSRule : public nsIStyleRule {
diff --git a/layout/style/nsICSSStyleRule.h b/layout/style/nsICSSStyleRule.h
index 0f3bd658ef7..c5836ea31cf 100644
--- a/layout/style/nsICSSStyleRule.h
+++ b/layout/style/nsICSSStyleRule.h
@@ -49,9 +49,7 @@
 #include "nsICSSRule.h"
 #include "nsString.h"
 #include "nsCOMPtr.h"
-#include "nsCSSProps.h"
 #include "nsCSSValue.h"
-#include "nsIAtom.h"
 #include "nsCSSPseudoElements.h"
 #include "nsCSSPseudoClasses.h"
 
@@ -289,10 +287,11 @@ private:
   nsCSSSelectorList& operator=(const nsCSSSelectorList& aCopy); 
 };
 
-// 1aae9e9d-21c3-4993-90b1-66aa6809f597
+// c6065b5e-4870-4dc5-9be3-747b6e317b25
 #define NS_ICSS_STYLE_RULE_IID \
-{ 0x1aae9e9d, 0x21c3, 0x4993, \
-  { 0x90, 0xb1, 0x66, 0xaa, 0x68, 0x09, 0xf5, 0x97 } }
+{ 0xc6065b5e, 0x4870, 0x4dc5, \
+  { 0x9b, 0xe3, 0x74, 0x7b, 0x6e, 0x31, 0x7b, 0x25 } }
+
 
 class nsICSSStyleRule : public nsICSSRule {
 public:
diff --git a/layout/style/nsIStyleRule.h b/layout/style/nsIStyleRule.h
index 66ef782c13b..819f169f563 100644
--- a/layout/style/nsIStyleRule.h
+++ b/layout/style/nsIStyleRule.h
@@ -103,12 +103,12 @@ public:
    * all needed data are found.  Thus overwriting non-empty data will
    * break CSS cascading rules.
    */
-  NS_IMETHOD MapRuleInfoInto(nsRuleData* aRuleData)=0;
+  virtual void MapRuleInfoInto(nsRuleData* aRuleData)=0;
 
   virtual nsIStyleRule* GetImportantRule(void) { return nsnull; }
 
 #ifdef DEBUG
-  NS_IMETHOD List(FILE* out = stdout, PRInt32 aIndent = 0) const = 0;
+  virtual void List(FILE* out = stdout, PRInt32 aIndent = 0) const = 0;
 #endif
 };
 
diff --git a/layout/style/nsStyleSet.cpp b/layout/style/nsStyleSet.cpp
index 9d1e07ab775..6e99d3da997 100644
--- a/layout/style/nsStyleSet.cpp
+++ b/layout/style/nsStyleSet.cpp
@@ -66,17 +66,15 @@ using namespace mozilla::dom;
 
 NS_IMPL_ISUPPORTS1(nsEmptyStyleRule, nsIStyleRule)
 
-NS_IMETHODIMP
+/* virtual */ void
 nsEmptyStyleRule::MapRuleInfoInto(nsRuleData* aRuleData)
 {
-  return NS_OK;
 }
 
 #ifdef DEBUG
-NS_IMETHODIMP
+/* virtual */ void
 nsEmptyStyleRule::List(FILE* out, PRInt32 aIndent) const
 {
-  return NS_OK;
 }
 #endif
 
diff --git a/layout/style/nsStyleSet.h b/layout/style/nsStyleSet.h
index aa876905a84..4bfe9ff89d1 100644
--- a/layout/style/nsStyleSet.h
+++ b/layout/style/nsStyleSet.h
@@ -66,9 +66,9 @@ struct RuleProcessorData;
 class nsEmptyStyleRule : public nsIStyleRule
 {
   NS_DECL_ISUPPORTS
-  NS_IMETHOD MapRuleInfoInto(nsRuleData* aRuleData);
+  virtual void MapRuleInfoInto(nsRuleData* aRuleData);
 #ifdef DEBUG
-  NS_IMETHOD List(FILE* out = stdout, PRInt32 aIndent = 0) const;
+  virtual void List(FILE* out = stdout, PRInt32 aIndent = 0) const;
 #endif
 };
 
diff --git a/layout/style/nsTransitionManager.cpp b/layout/style/nsTransitionManager.cpp
index 5af09d9ac6c..82c95fd3693 100644
--- a/layout/style/nsTransitionManager.cpp
+++ b/layout/style/nsTransitionManager.cpp
@@ -106,9 +106,9 @@ public:
   NS_DECL_ISUPPORTS
 
   // nsIStyleRule implementation
-  NS_IMETHOD MapRuleInfoInto(nsRuleData* aRuleData);
+  virtual void MapRuleInfoInto(nsRuleData* aRuleData);
 #ifdef DEBUG
-  NS_IMETHOD List(FILE* out = stdout, PRInt32 aIndent = 0) const;
+  virtual void List(FILE* out = stdout, PRInt32 aIndent = 0) const;
 #endif
 
   ElementTransitionsStyleRule(ElementTransitions *aOwner,
@@ -142,9 +142,9 @@ public:
   NS_DECL_ISUPPORTS
 
   // nsIStyleRule implementation
-  NS_IMETHOD MapRuleInfoInto(nsRuleData* aRuleData);
+  virtual void MapRuleInfoInto(nsRuleData* aRuleData);
 #ifdef DEBUG
-  NS_IMETHOD List(FILE* out = stdout, PRInt32 aIndent = 0) const;
+  virtual void List(FILE* out = stdout, PRInt32 aIndent = 0) const;
 #endif
 
   void CoverValue(nsCSSProperty aProperty, nsStyleAnimation::Value &aStartValue)
@@ -217,18 +217,22 @@ ElementTransitionsPropertyDtor(void           *aObject,
 
 NS_IMPL_ISUPPORTS1(ElementTransitionsStyleRule, nsIStyleRule)
 
-NS_IMETHODIMP
+/* virtual */ void
 ElementTransitionsStyleRule::MapRuleInfoInto(nsRuleData* aRuleData)
 {
   nsStyleContext *contextParent = aRuleData->mStyleContext->GetParent();
   if (contextParent && contextParent->HasPseudoElementData()) {
     // Don't apply transitions to things inside of pseudo-elements.
     // FIXME (Bug 522599): Add tests for this.
-    return NS_OK;
+    return;
   }
 
   ElementTransitions *et = ElementData();
-  NS_ENSURE_TRUE(et, NS_OK); // FIXME (Bug 522597): Why can this be null?
+  if (NS_UNLIKELY(!et)) { // FIXME (Bug 522597): Why can this be null? 
+     NS_WARNING("ElementData returned null");
+     return;
+  }
+
   for (PRUint32 i = 0, i_end = et->mPropertyTransitions.Length();
        i < i_end; ++i)
   {
@@ -267,16 +271,13 @@ ElementTransitionsStyleRule::MapRuleInfoInto(nsRuleData* aRuleData)
       NS_ABORT_IF_FALSE(ok, "could not store computed value");
     }
   }
-
-  return NS_OK;
 }
 
 #ifdef DEBUG
-NS_IMETHODIMP
+/* virtual */ void
 ElementTransitionsStyleRule::List(FILE* out, PRInt32 aIndent) const
 {
   // WRITE ME?
-  return NS_OK;
 }
 #endif
 
@@ -310,7 +311,7 @@ ElementTransitions::EnsureStyleRuleFor(TimeStamp aRefreshTime)
 
 NS_IMPL_ISUPPORTS1(CoverTransitionStartStyleRule, nsIStyleRule)
 
-NS_IMETHODIMP
+/* virtual */ void
 CoverTransitionStartStyleRule::MapRuleInfoInto(nsRuleData* aRuleData)
 {
   for (PRUint32 i = 0, i_end = mCoveredValues.Length(); i < i_end; ++i) {
@@ -328,16 +329,13 @@ CoverTransitionStartStyleRule::MapRuleInfoInto(nsRuleData* aRuleData)
       NS_ABORT_IF_FALSE(ok, "could not store computed value");
     }
   }
-
-  return NS_OK;
 }
 
 #ifdef DEBUG
-NS_IMETHODIMP
+/* virtual */ void
 CoverTransitionStartStyleRule::List(FILE* out, PRInt32 aIndent) const
 {
   // WRITE ME?
-  return NS_OK;
 }
 #endif