Bug 996796 patch 23 - Make transition manager ignore StyleContextChanged notifications during an animation-only style update. r=heycam

This will be necessary when we use the restyle tracker for the
animation-only style flush.

layout/base/RestyleManager.cpp

@@ -1574,8 +1574,15 @@ RestyleManager::UpdateOnlyAnimationStyles()
   }
   mLastUpdateForThrottledAnimations = now;
 
-  mPresContext->TransitionManager()->UpdateAllThrottledStyles();
-  mPresContext->AnimationManager()->UpdateAllThrottledStyles();
+  nsTransitionManager* transitionManager = mPresContext->TransitionManager();
+  nsAnimationManager* animationManager = mPresContext->AnimationManager();
+
+  transitionManager->SetInAnimationOnlyStyleUpdate(true);
+
+  transitionManager->UpdateAllThrottledStyles();
+  animationManager->UpdateAllThrottledStyles();
+
+  transitionManager->SetInAnimationOnlyStyleUpdate(false);
 }
 
 void

layout/style/nsTransitionManager.cpp

@@ -163,6 +163,15 @@ nsTransitionManager::StyleContextChanged(dom::Element *aElement,
                       aNewStyleContext->HasPseudoElementData(),
                   "pseudo type mismatch");
 
+  if (mInAnimationOnlyStyleUpdate) {
+    // If we're doing an animation-only style update, return, since the
+    // purpose of an animation-only style update is to update only the
+    // animation styles so that we don't consider style changes
+    // resulting from changes in the animation time for starting a
+    // transition.
+    return nullptr;
+  }
+
   if (!mPresContext->IsDynamic()) {
     // For print or print preview, ignore transitions.
     return nullptr;

layout/style/nsTransitionManager.h

@@ -67,6 +67,7 @@ class nsTransitionManager MOZ_FINAL
 public:
   nsTransitionManager(nsPresContext *aPresContext)
     : mozilla::css::CommonAnimationManager(aPresContext)
+    , mInAnimationOnlyStyleUpdate(false)
   {
   }
 
@@ -117,6 +118,10 @@ public:
                         nsStyleContext *aOldStyleContext,
                         nsStyleContext *aNewStyleContext);
 
+  void SetInAnimationOnlyStyleUpdate(bool aInAnimationOnlyUpdate) {
+    mInAnimationOnlyStyleUpdate = aInAnimationOnlyUpdate;
+  }
+
   // nsIStyleRuleProcessor (parts)
   virtual void RulesMatching(ElementRuleProcessorData* aData) MOZ_OVERRIDE;
   virtual void RulesMatching(PseudoElementRuleProcessorData* aData) MOZ_OVERRIDE;
@@ -184,6 +189,8 @@ private:
                                        nsStyleContext* aParentStyle,
                                        nsStyleChangeList &aChangeList);
   void UpdateAllThrottledStylesInternal();
+
+  bool mInAnimationOnlyStyleUpdate;
 };
 
 #endif /* !defined(nsTransitionManager_h_) */