Bug 1025709 part 10 - Move active layer notification out of CanPerformOnCompositorThread to call sites; r=heycam

A previous patch moved CanPerformOnCompositorThread to
CommonElementAnimationData including a FIXME saying that active layer
notification should happen at call sites. Now that the code for
GetAnimationsForCompositor is common, we can do the active layer notification
there.

layout/style/AnimationCommon.cpp

@@ -92,6 +92,18 @@ CommonAnimationManager::GetAnimationsForCompositor(nsIContent* aContent,
         CommonElementAnimationData::CanAnimate_AllowPartial)) {
     return nullptr;
   }
+
+  // This animation can be done on the compositor.
+  // Mark the frame as active, in case we are able to throttle this animation.
+  nsIFrame* frame = nsLayoutUtils::GetStyleFrame(animations->mElement);
+  if (frame) {
+    if (aProperty == eCSSProperty_opacity) {
+      ActiveLayerTracker::NotifyAnimated(frame, eCSSProperty_opacity);
+    } else if (aProperty == eCSSProperty_transform) {
+      ActiveLayerTracker::NotifyAnimated(frame, eCSSProperty_transform);
+    }
+  }
+
   return animations;
 }
 
@@ -654,8 +666,6 @@ CommonElementAnimationData::CanPerformOnCompositorThread(
     }
   }
 
-  bool hasOpacity = false;
-  bool hasTransform = false;
   bool existsProperty = false;
   for (uint32_t animIdx = mAnimations.Length(); animIdx-- != 0; ) {
     const ElementAnimation* anim = mAnimations[animIdx];
@@ -674,11 +684,6 @@ CommonElementAnimationData::CanPerformOnCompositorThread(
           IsCompositorAnimationDisabledForFrame(frame)) {
         return false;
       }
-      if (prop.mProperty == eCSSProperty_opacity) {
-        hasOpacity = true;
-      } else if (prop.mProperty == eCSSProperty_transform) {
-        hasTransform = true;
-      }
     }
   }
 
@@ -687,14 +692,6 @@ CommonElementAnimationData::CanPerformOnCompositorThread(
     return false;
   }
 
-  // This animation can be done on the compositor.  Mark the frame as active, in
-  // case we are able to throttle this animation.
-  if (hasOpacity) {
-    ActiveLayerTracker::NotifyAnimated(frame, eCSSProperty_opacity);
-  }
-  if (hasTransform) {
-    ActiveLayerTracker::NotifyAnimated(frame, eCSSProperty_transform);
-  }
   return true;
 }
 

layout/style/AnimationCommon.h

@@ -75,6 +75,8 @@ protected:
   virtual void ElementDataRemoved() = 0;
   void RemoveAllElementData();
 
+  // When this returns a value other than nullptr, it also,
+  // as a side-effect, notifies the ActiveLayerTracker.
   static CommonElementAnimationData*
   GetAnimationsForCompositor(nsIContent* aContent,
                              nsIAtom* aElementProperty,
@@ -469,10 +471,6 @@ struct CommonElementAnimationData : public PRCList
   // time can be fully represented by data sent to the compositor.
   // (This is useful for determining whether throttle the animation
   // (suppress main-thread style updates).)
-  //
-  // Note that when CanPerformOnCompositorThread returns true, it also,
-  // as a side-effect, notifies the ActiveLayerTracker.  FIXME:  This
-  // should probably move to the relevant callers.
   bool CanPerformOnCompositorThread(CanAnimateFlags aFlags) const;
   bool HasAnimationOfProperty(nsCSSProperty aProperty) const;