SVG: Moving animating <svg> to other iframe should not crash.

Source/core/svg/SVGDocumentExtensions.cpp

Index: Source/core/svg/SVGDocumentExtensions.cpp
diff --git a/Source/core/svg/SVGDocumentExtensions.cpp b/Source/core/svg/SVGDocumentExtensions.cpp
index b8665f61731e5afa1273dd05fe3b8fd7a5e7a7f5..bf28cc21f5f24a112c4381a7a47891f7a2868b6b 100644
--- a/Source/core/svg/SVGDocumentExtensions.cpp
+++ b/Source/core/svg/SVGDocumentExtensions.cpp
@@ -111,8 +111,11 @@ void SVGDocumentExtensions::startAnimations()
     WillBeHeapVector<RefPtrWillBeMember<SVGSVGElement> > timeContainers;
     timeContainers.appendRange(m_timeContainers.begin(), m_timeContainers.end());
     WillBeHeapVector<RefPtrWillBeMember<SVGSVGElement> >::iterator end = timeContainers.end();
-    for (WillBeHeapVector<RefPtrWillBeMember<SVGSVGElement> >::iterator itr = timeContainers.begin(); itr != end; ++itr)
-        (*itr)->timeContainer()->begin();
+    for (WillBeHeapVector<RefPtrWillBeMember<SVGSVGElement> >::iterator itr = timeContainers.begin(); itr != end; ++itr) {
+        SMILTimeContainer* timeContainer = (*itr)->timeContainer();
+        if (!timeContainer->isStarted())
+            timeContainer->begin();
+    }
 }
 
 void SVGDocumentExtensions::pauseAnimations()