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

We create ScrollingCoordinator for pages with non-local frames, but it's noop in functionality because of guards:

if (!m_page->mainFrame()->isLocalFrame())
  return;

Let's align the behavior with the rest of ScrollingCoordinator code. Otherwise it crashes browser tests.

BUG=394777

Review URL: https://codereview.chromium.org/1304213003

git-svn-id: svn://svn.chromium.org/blink/trunk@201945 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/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()));
+        }
     }
 }