Compositor Animations: Do not create compositor animation timeline for remote frames

Source/core/page/scrolling/ScrollingCoordinator.cpp

Index: Source/core/page/scrolling/ScrollingCoordinator.cpp
diff --git a/Source/core/page/scrolling/ScrollingCoordinator.cpp b/Source/core/page/scrolling/ScrollingCoordinator.cpp
index 6a9fb887b6105b3637e5a6f365c6cdef15d57b7e..c2addffbc8220326dc46e682af19e1eaa9d6434c 100644
--- a/Source/core/page/scrolling/ScrollingCoordinator.cpp
+++ b/Source/core/page/scrolling/ScrollingCoordinator.cpp
@@ -96,10 +96,11 @@ ScrollingCoordinator::ScrollingCoordinator(Page* page)
 {
     if (RuntimeEnabledFeatures::compositorAnimationTimelinesEnabled() && Platform::current()->isThreadedAnimationEnabled()) {
         ASSERT(m_page);
-        ASSERT(m_page->mainFrame()->isLocalFrame());
-        ASSERT(Platform::current()->compositorSupport());
-        m_programmaticScrollAnimatorTimeline = adoptPtr(Platform::current()->compositorSupport()->createAnimationTimeline());
-        m_page->chromeClient().attachCompositorAnimationTimeline(m_programmaticScrollAnimatorTimeline.get(), toLocalFrame(m_page->mainFrame()));
+        if (m_page->mainFrame()->isLocalFrame()) {
+            ASSERT(Platform::current()->compositorSupport());
+            m_programmaticScrollAnimatorTimeline = adoptPtr(Platform::current()->compositorSupport()->createAnimationTimeline());
+            m_page->chromeClient().attachCompositorAnimationTimeline(m_programmaticScrollAnimatorTimeline.get(), toLocalFrame(m_page->mainFrame()));
+        }
     }
 }