Bug 489581 - Reduce Addref/Release when calling event handlers, r+sr=jst

content/base/public/nsContentUtils.h

@@ -1362,8 +1362,8 @@ public:
   static nsresult ProcessViewportInfo(nsIDocument *aDocument,
                                       const nsAString &viewportInfo);
 
-  static nsresult GetContextForEventHandlers(nsINode* aNode,
-                                             nsIScriptContext** aContext);
+  static nsIScriptContext* GetContextForEventHandlers(nsINode* aNode,
+                                                      nsresult* aRv);
 
   static JSContext *GetCurrentJSContext();
 

content/base/src/nsContentUtils.cpp

@@ -2710,8 +2710,9 @@ nsCxPusher::Push(nsPIDOMEventTarget *aCurrentTarget)
   }
 
   NS_ENSURE_TRUE(aCurrentTarget, PR_FALSE);
-  nsCOMPtr<nsIScriptContext> scx;
-  nsresult rv = aCurrentTarget->GetContextForEventHandlers(getter_AddRefs(scx));
+  nsresult rv;
+  nsIScriptContext* scx =
+    aCurrentTarget->GetContextForEventHandlers(&rv);
   NS_ENSURE_SUCCESS(rv, PR_FALSE);
 
   if (!scx) {
@@ -4503,26 +4504,38 @@ nsContentUtils::URIIsLocalFile(nsIURI *aURI)
 }
 
 /* static */
-nsresult
+nsIScriptContext*
 nsContentUtils::GetContextForEventHandlers(nsINode* aNode,
-                                           nsIScriptContext** aContext)
+                                           nsresult* aRv)
 {
-  *aContext = nsnull;
+  *aRv = NS_OK;
   nsIDocument* ownerDoc = aNode->GetOwnerDoc();
-  NS_ENSURE_STATE(ownerDoc);
-  nsCOMPtr<nsIScriptGlobalObject> sgo;
-  PRBool hasHadScriptObject = PR_TRUE;
-  sgo = ownerDoc->GetScriptHandlingObject(hasHadScriptObject);
-  // It is bad if the document doesn't have event handling context,
-  // but it used to have one.
-  NS_ENSURE_STATE(sgo || !hasHadScriptObject);
-  if (sgo) {
-    NS_IF_ADDREF(*aContext = sgo->GetContext());
-    // Bad, no context from script global object!
-    NS_ENSURE_STATE(*aContext);
+  if (!ownerDoc) {
+    *aRv = NS_ERROR_UNEXPECTED;
+    return nsnull;
   }
 
-  return NS_OK;
+  PRBool hasHadScriptObject = PR_TRUE;
+  nsIScriptGlobalObject* sgo =
+    ownerDoc->GetScriptHandlingObject(hasHadScriptObject);
+  // It is bad if the document doesn't have event handling context,
+  // but it used to have one.
+  if (!sgo && hasHadScriptObject) {
+    *aRv = NS_ERROR_UNEXPECTED;
+    return nsnull;
+  }
+
+  if (sgo) {
+    nsIScriptContext* scx = sgo->GetContext();
+    // Bad, no context from script global object!
+    if (!scx) {
+      *aRv = NS_ERROR_UNEXPECTED;
+      return nsnull;
+    }
+    return scx;
+  }
+
+  return nsnull;
 }
 
 /* static */

content/base/src/nsDOMAttribute.h

@@ -109,9 +109,9 @@ public:
   virtual nsresult RemoveEventListenerByIID(nsIDOMEventListener *aListener,
                                             const nsIID& aIID);
   virtual nsresult GetSystemEventGroup(nsIDOMEventGroup** aGroup);
-  virtual nsresult GetContextForEventHandlers(nsIScriptContext** aContext)
+  virtual nsIScriptContext* GetContextForEventHandlers(nsresult* aRv)
   {
-    return nsContentUtils::GetContextForEventHandlers(this, aContext);
+    return nsContentUtils::GetContextForEventHandlers(this, aRv);
   }
   virtual nsresult Clone(nsINodeInfo *aNodeInfo, nsINode **aResult) const;
 

content/base/src/nsDocument.h

@@ -821,9 +821,9 @@ public:
   virtual nsresult RemoveEventListenerByIID(nsIDOMEventListener *aListener,
                                             const nsIID& aIID);
   virtual nsresult GetSystemEventGroup(nsIDOMEventGroup** aGroup);
-  virtual nsresult GetContextForEventHandlers(nsIScriptContext** aContext)
+  virtual nsIScriptContext* GetContextForEventHandlers(nsresult* aRv)
   {
-    return nsContentUtils::GetContextForEventHandlers(this, aContext);
+    return nsContentUtils::GetContextForEventHandlers(this, aRv);
   }
   virtual nsresult Clone(nsINodeInfo *aNodeInfo, nsINode **aResult) const
   {

content/base/src/nsGenericDOMDataNode.h

@@ -179,9 +179,9 @@ public:
   virtual nsresult RemoveEventListenerByIID(nsIDOMEventListener *aListener,
                                             const nsIID& aIID);
   virtual nsresult GetSystemEventGroup(nsIDOMEventGroup** aGroup);
-  virtual nsresult GetContextForEventHandlers(nsIScriptContext** aContext)
+  virtual nsIScriptContext* GetContextForEventHandlers(nsresult* aRv)
   {
-    return nsContentUtils::GetContextForEventHandlers(this, aContext);
+    return nsContentUtils::GetContextForEventHandlers(this, aRv);
   }
 
   // Implementation for nsIContent

content/base/src/nsGenericElement.h

@@ -366,9 +366,9 @@ public:
   virtual nsresult RemoveEventListenerByIID(nsIDOMEventListener *aListener,
                                             const nsIID& aIID);
   virtual nsresult GetSystemEventGroup(nsIDOMEventGroup** aGroup);
-  virtual nsresult GetContextForEventHandlers(nsIScriptContext** aContext)
+  virtual nsIScriptContext* GetContextForEventHandlers(nsresult* aRv)
   {
-    return nsContentUtils::GetContextForEventHandlers(this, aContext);
+    return nsContentUtils::GetContextForEventHandlers(this, aRv);
   }
 
   // nsIContent interface methods

content/base/src/nsXMLHttpRequest.cpp

@@ -589,8 +589,10 @@ nsXHREventTarget::AddEventListener(const nsAString& aType,
                                    nsIDOMEventListener* aListener,
                                    PRBool aUseCapture)
 {
-  nsCOMPtr<nsIScriptContext> context;
-  GetContextForEventHandlers(getter_AddRefs(context));
+  nsresult rv;
+  nsIScriptContext* context =
+    GetContextForEventHandlers(&rv);
+  NS_ENSURE_SUCCESS(rv, rv);
   nsCOMPtr<nsIDocument> doc = GetDocumentFromScriptContext(context);
   PRBool wantsUntrusted = doc && !nsContentUtils::IsChromeDoc(doc);
   return AddEventListener(aType, aListener, aUseCapture, wantsUntrusted);
@@ -826,13 +828,14 @@ nsXHREventTarget::GetSystemEventGroup(nsIDOMEventGroup** aGroup)
   return rv;
 }
 
-nsresult
-nsXHREventTarget::GetContextForEventHandlers(nsIScriptContext** aContext)
+nsIScriptContext*
+nsXHREventTarget::GetContextForEventHandlers(nsresult* aRv)
 {
-  nsresult rv = CheckInnerWindowCorrectness();
-  NS_ENSURE_SUCCESS(rv, rv);
-  NS_IF_ADDREF(*aContext = mScriptContext);
-  return NS_OK;
+  *aRv = CheckInnerWindowCorrectness();
+  if (NS_FAILED(*aRv)) {
+    return nsnull;
+  }
+  return mScriptContext;
 }
 
 /////////////////////////////////////////////
@@ -3357,8 +3360,10 @@ NS_IMETHODIMP
 nsXMLHttpRequest::GetUpload(nsIXMLHttpRequestUpload** aUpload)
 {
   *aUpload = nsnull;
-  nsCOMPtr<nsIScriptContext> scriptContext;
-  nsresult rv = GetContextForEventHandlers(getter_AddRefs(scriptContext));
+
+  nsresult rv;
+  nsIScriptContext* scriptContext =
+    GetContextForEventHandlers(&rv);
   NS_ENSURE_SUCCESS(rv, rv);
   if (!mUpload) {
     mUpload = new nsXMLHttpRequestUpload(mOwner, scriptContext);

content/base/src/nsXMLHttpRequest.h

@@ -186,7 +186,7 @@ public:
   virtual nsresult RemoveEventListenerByIID(nsIDOMEventListener *aListener,
                                             const nsIID& aIID);
   virtual nsresult GetSystemEventGroup(nsIDOMEventGroup** aGroup);
-  virtual nsresult GetContextForEventHandlers(nsIScriptContext** aContext);
+  virtual nsIScriptContext* GetContextForEventHandlers(nsresult* aRv);
 
   PRBool HasListenersFor(const nsAString& aType)
   {

content/events/public/nsPIDOMEventTarget.h

@@ -52,8 +52,8 @@ class nsIScriptContext;
 
 // 25982813-af2e-4ab6-b512-e6c6ada6d0ec
 #define NS_PIDOMEVENTTARGET_IID \
-  { 0x25982813, 0xaf2e, 0x4ab6, \
-    { 0xb5, 0x12, 0xe6, 0xc6, 0xad, 0xa6, 0xd0, 0xec } }
+  { 0x358f2990, 0x5107, 0x49ba, \
+    { 0x88, 0x94, 0x14, 0x34, 0x86, 0xd5, 0x99, 0x85 } }
 
 class nsPIDOMEventTarget : public nsISupports
 {
@@ -163,8 +163,9 @@ public:
   /**
    * Get the script context in which the event handlers should be run.
    * May return null.
+   * @note Caller *must* check the value of aRv.
    */
-  virtual nsresult GetContextForEventHandlers(nsIScriptContext** aContext) = 0;
+  virtual nsIScriptContext* GetContextForEventHandlers(nsresult* aRv) = 0;
 };
 
 NS_DEFINE_STATIC_IID_ACCESSOR(nsPIDOMEventTarget, NS_PIDOMEVENTTARGET_IID)

dom/base/nsGlobalWindow.cpp

@@ -6456,13 +6456,12 @@ nsGlobalWindow::GetSystemEventGroup(nsIDOMEventGroup **aGroup)
   return NS_ERROR_FAILURE;
 }
 
-nsresult
-nsGlobalWindow::GetContextForEventHandlers(nsIScriptContext** aContext)
+nsIScriptContext*
+nsGlobalWindow::GetContextForEventHandlers(nsresult* aRv)
 {
-  NS_IF_ADDREF(*aContext = GetContext());
-  // Bad, no context from script global object!
-  NS_ENSURE_STATE(*aContext);
-  return NS_OK;
+  nsIScriptContext* scx = GetContext();
+  *aRv = scx ? NS_OK : NS_ERROR_UNEXPECTED;
+  return scx;
 }
 
 //*****************************************************************************

dom/base/nsGlobalWindow.h

@@ -335,7 +335,7 @@ public:
   virtual NS_HIDDEN_(nsresult) RemoveEventListenerByIID(nsIDOMEventListener *aListener,
                                                         const nsIID& aIID);
   virtual NS_HIDDEN_(nsresult) GetSystemEventGroup(nsIDOMEventGroup** aGroup);
-  virtual NS_HIDDEN_(nsresult) GetContextForEventHandlers(nsIScriptContext** aContext);
+  virtual NS_HIDDEN_(nsIScriptContext*) GetContextForEventHandlers(nsresult* aRv);
 
   virtual NS_HIDDEN_(void) SetDocShell(nsIDocShell* aDocShell);
   virtual NS_HIDDEN_(nsresult) SetNewDocument(nsIDocument *aDocument,

dom/base/nsWindowRoot.h

@@ -83,10 +83,10 @@ public:
   virtual nsresult RemoveEventListenerByIID(nsIDOMEventListener *aListener,
                                             const nsIID& aIID);
   virtual nsresult GetSystemEventGroup(nsIDOMEventGroup** aGroup);
-  virtual nsresult GetContextForEventHandlers(nsIScriptContext** aContext)
+  virtual nsIScriptContext* GetContextForEventHandlers(nsresult* aRv)
   {
-    *aContext = nsnull;
-    return NS_OK;
+    *aRv = NS_OK;
+    return nsnull;
   }
 
   // nsPIWindowRoot