Don't schedule a wake-up if the timeline hasn't started

Before the timeline has started we shouldn't update animations. This
makes resume() symmetric with pause().

BUG=631879

Review-Url: https://codereview.chromium.org/2254303005
Cr-Commit-Position: refs/heads/master@{#413336}

third_party/WebKit/Source/core/svg/animation/SMILTimeContainer.cpp

@@ -214,9 +214,10 @@ void SMILTimeContainer::resume()
 
     m_paused = false;
 
-    if (isStarted())
-        synchronizeToDocumentTimeline();
+    if (!isStarted())
+        return;
 
+    synchronizeToDocumentTimeline();
     scheduleWakeUp(0, SynchronizeAnimations);
 }