Bug 1046055 part 4 - Add HasCurrentAnimationsForProperty to nsLayoutUtils; r=dbaron

This patch adds a method to nsLayoutUtils, alongside the existing
HasCurrentAnimations, that returns true if there exists an unfinished animation
on the element for the specified property.

layout/base/nsLayoutUtils.cpp

@@ -405,6 +405,26 @@ nsLayoutUtils::HasCurrentAnimations(nsIContent* aContent,
   return (collection && collection->HasCurrentAnimations());
 }
 
+bool
+nsLayoutUtils::HasCurrentAnimationsForProperty(nsIContent* aContent,
+                                               nsCSSProperty aProperty)
+{
+  if (!aContent->MayHaveAnimations())
+    return false;
+
+  static nsIAtom* const sAnimProps[] = { nsGkAtoms::transitionsProperty,
+                                         nsGkAtoms::animationsProperty,
+                                         nullptr };
+  for (nsIAtom* const* animProp = sAnimProps; *animProp; animProp++) {
+    AnimationPlayerCollection* collection =
+      static_cast<AnimationPlayerCollection*>(aContent->GetProperty(*animProp));
+    if (collection && collection->HasCurrentAnimationsForProperty(aProperty))
+      return true;
+  }
+
+  return false;
+}
+
 static gfxSize
 GetScaleForValue(const StyleAnimationValue& aValue, nsIFrame* aFrame)
 {

layout/base/nsLayoutUtils.h

@@ -1879,13 +1879,21 @@ public:
   static bool HasAnimations(nsIContent* aContent, nsCSSProperty aProperty);
 
   /**
-   * Returns true if the content node has any current animations or transitions.
+   * Returns true if the content node has any current animations or transitions
+   * (depending on the value of |aAnimationProperty|).
    * A current animation is any animation that has not yet finished playing
    * including paused animations.
    */
   static bool HasCurrentAnimations(nsIContent* aContent,
                                    nsIAtom* aAnimationProperty);
 
+  /**
+   * Returns true if the content node has any current animations or transitions
+   * for the specified property.
+   */
+  static bool HasCurrentAnimationsForProperty(nsIContent* aContent,
+                                              nsCSSProperty aProperty);
+
   /**
    * Checks if off-main-thread animations are enabled.
    */