Bug 625289 patch 4 - Add member variable to restyle manager for currently reframing style contexts. r=heycam

layout/base/RestyleManager.cpp

@@ -55,6 +55,7 @@ RestyleManager::RestyleManager(nsPresContext* aPresContext)
   , mLastUpdateForThrottledAnimations(aPresContext->RefreshDriver()->
                                         MostRecentRefresh())
   , mAnimationGeneration(0)
+  , mReframingStyleContexts(nullptr)
   , mPendingRestyles(ELEMENT_HAS_PENDING_RESTYLE |
                      ELEMENT_IS_POTENTIAL_RESTYLE_ROOT)
   , mPendingAnimationRestyles(ELEMENT_HAS_PENDING_ANIMATION_RESTYLE |

layout/base/RestyleManager.h

@@ -42,6 +42,8 @@ private:
   // Private destructor, to discourage deletion outside of Release():
   ~RestyleManager()
   {
+    MOZ_ASSERT(!mReframingStyleContexts,
+               "temporary member should be nulled out before destruction");
   }
 
 public:
@@ -150,6 +152,14 @@ public:
     ReframingStyleContextTable mAfterPseudoContexts;
   };
 
+  /**
+   * Return the current ReframingStyleContexts struct, or null if we're
+   * not currently in a restyling operation.
+   */
+  ReframingStyleContexts* GetReframingStyleContexts() {
+    return mReframingStyleContexts;
+  }
+
 private:
   void RestyleForEmptyChange(Element* aContainer);
 
@@ -331,6 +341,8 @@ private:
   // Used to keep the layer and animation manager in sync.
   uint64_t mAnimationGeneration;
 
+  ReframingStyleContexts* mReframingStyleContexts;
+
   RestyleTracker mPendingRestyles;
   RestyleTracker mPendingAnimationRestyles;
 };