Bug 996796 patch 2 - Change the public API to updating main-thread-suppressed animation styles (miniflush) in preparation for refactoring how it works. r=birtles

Later patches will combine the coalescing of restyling between the
miniflush performed for animations and for transitions into a single
RestyleTracker, which will coalesce the work better.  This patch changes
the API exposed for doing that so that the coalescing patch will contain
only the internals.

layout/base/RestyleManager.cpp

@@ -1468,8 +1468,7 @@ RestyleManager::ProcessPendingRestyles()
   if (nsLayoutUtils::AreAsyncAnimationsEnabled() &&
       mPendingRestyles.Count() > 0) {
     ++mAnimationGeneration;
-    mPresContext->TransitionManager()->UpdateAllThrottledStyles();
-    mPresContext->AnimationManager()->UpdateAllThrottledStyles();
+    UpdateOnlyAnimationStyles();
   }
 
   mPendingRestyles.ProcessRestyles();
@@ -1529,6 +1528,13 @@ RestyleManager::EndProcessingRestyles()
 #endif
 }
 
+void
+RestyleManager::UpdateOnlyAnimationStyles()
+{
+  mPresContext->TransitionManager()->UpdateAllThrottledStyles();
+  mPresContext->AnimationManager()->UpdateAllThrottledStyles();
+}
+
 void
 RestyleManager::PostRestyleEventCommon(Element* aElement,
                                        nsRestyleHint aRestyleHint,

layout/base/RestyleManager.h

@@ -160,6 +160,12 @@ public:
   void BeginProcessingRestyles();
   void EndProcessingRestyles();
 
+  // Update styles for animations that are running on the compositor and
+  // whose updating is suppressed on the main thread (to save
+  // unnecessary work), while leaving all other aspects of style
+  // out-of-date.
+  void UpdateOnlyAnimationStyles();
+
   // Rebuilds all style data by throwing out the old rule tree and
   // building a new one, and additionally applying aExtraHint (which
   // must not contain nsChangeHint_ReconstructFrame) to the root frame.

layout/base/nsPresShell.cpp

@@ -6689,8 +6689,7 @@ FlushThrottledStyles(nsIDocument *aDocument, void *aData)
   if (shell && shell->IsVisible()) {
     nsPresContext* presContext = shell->GetPresContext();
     if (presContext) {
-      presContext->TransitionManager()->UpdateAllThrottledStyles();
-      presContext->AnimationManager()->UpdateAllThrottledStyles();
+      presContext->RestyleManager()->UpdateOnlyAnimationStyles();
     }
   }