Bug 709256 part 1. Fast-path RestyleTracker::ProcessRestyles when there aren't any restyles to process. r=roc

layout/base/RestyleTracker.cpp

@@ -166,7 +166,7 @@ RestyleTracker::ProcessOneRestyle(Element* aElement,
 }
 
 void
-RestyleTracker::ProcessRestyles()
+RestyleTracker::DoProcessRestyles()
 {
   SAMPLE_LABEL("CSS", "ProcessRestyles");
   // Make sure to not rebuild quote or counter lists while we're

layout/base/RestyleTracker.h

@@ -94,7 +94,13 @@ public:
   /**
    * Process the restyles we've been tracking.
    */
-  void ProcessRestyles();
+  void ProcessRestyles() {
+    // Fast-path the common case (esp. for the animation restyle
+    // tracker) of not having anything to do.
+    if (mPendingRestyles.Count()) {
+      DoProcessRestyles();
+    }
+  }
 
   // Return our ELEMENT_HAS_PENDING_(ANIMATION_)RESTYLE bit
   PRUint32 RestyleBit() const {
@@ -143,6 +149,11 @@ private:
                                 nsRestyleHint aRestyleHint,
                                 nsChangeHint aChangeHint);
 
+  /**
+   * The guts of our restyle processing.
+   */
+  void DoProcessRestyles();
+
   typedef nsDataHashtable<nsISupportsHashKey, RestyleData> PendingRestyleTable;
   typedef nsAutoTArray< nsRefPtr<Element>, 32> RestyleRootArray;
   // Our restyle bits.  These will be a subset of ELEMENT_ALL_RESTYLE_FLAGS, and