Blink Compositor Animation: Introduce CompositorAnimationHost correctly.

third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights
  * reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@gmail.com>
@@ skipping 126 matching lines @@
       frame->eventHandler().resizeScrollableAreaDestroyed();
   }
 
   if (LocalFrame* frame = box().frame()) {
     if (FrameView* frameView = frame->view()) {
       frameView->removeScrollableArea(this);
       frameView->removeAnimatingScrollableArea(this);
     }
   }
 
-  if (box().frame() && box().frame()->page()) {
-    if (ScrollingCoordinator* scrollingCoordinator =
-            box().frame()->page()->scrollingCoordinator())
-      scrollingCoordinator->willDestroyScrollableArea(this);
-  }
+  if (ScrollingCoordinator* scrollingCoordinator = getScrollingCoordinator())
+    scrollingCoordinator->willDestroyScrollableArea(this);
 
   if (!box().documentBeingDestroyed()) {
     Node* node = box().node();
     // FIXME: Make setSavedLayerScrollOffset take DoubleSize. crbug.com/414283.
     if (node && node->isElementNode())
       toElement(node)->setSavedLayerScrollOffset(m_scrollOffset);
   }
 
   if (LocalFrame* frame = box().frame()) {
     if (FrameView* frameView = frame->view())
@@ skipping 1526 matching lines @@
       layer()->compositedLayerMapping()->setNeedsGraphicsLayerUpdate(
           GraphicsLayerUpdateSubtree);
       compositor->setNeedsCompositingUpdate(
           CompositingUpdateAfterGeometryChange);
     } else {
       layer()->setNeedsCompositingInputsUpdate();
     }
   }
 }
 
+ScrollingCoordinator* PaintLayerScrollableArea::getScrollingCoordinator()
+    const {
+  LocalFrame* frame = box().frame();
+  if (!frame)
+    return nullptr;
+
+  Page* page = frame->page();
+  if (!page)
+    return nullptr;
+
+  return page->scrollingCoordinator();
+}
+
 bool PaintLayerScrollableArea::usesCompositedScrolling() const {
   // See https://codereview.chromium.org/176633003/ for the tests that fail
   // without this disabler.
   DisableCompositingQueryAsserts disabler;
   return layer()->hasCompositedLayerMapping() &&
          layer()->compositedLayerMapping()->scrollingLayer();
 }
 
 bool PaintLayerScrollableArea::shouldScrollOnMainThread() const {
-  if (LocalFrame* frame = box().frame()) {
-    if (Page* page = frame->page()) {
-      if (page->scrollingCoordinator()
-              ->shouldUpdateScrollLayerPositionOnMainThread())
-        return true;
-    }
+  if (ScrollingCoordinator* scrollingCoordinator = getScrollingCoordinator()) {
+    if (scrollingCoordinator->shouldUpdateScrollLayerPositionOnMainThread())
+      return true;
   }
   return ScrollableArea::shouldScrollOnMainThread();
 }
 
 static bool layerNeedsCompositedScrolling(
     PaintLayerScrollableArea::LCDTextMode mode,
     const PaintLayer* layer) {
   if (!layer->scrollsOverflow())
     return false;
 
@@ skipping 64 matching lines @@
 
 Widget* PaintLayerScrollableArea::getWidget() {
   return box().frame()->view();
 }
 
 void PaintLayerScrollableArea::resetRebuildScrollbarLayerFlags() {
   m_rebuildHorizontalScrollbarLayer = false;
   m_rebuildVerticalScrollbarLayer = false;
 }
 
+CompositorAnimationHost* PaintLayerScrollableArea::compositorAnimationHost()
+    const {
+  if (ScrollingCoordinator* coordinator = getScrollingCoordinator())
+    return coordinator->compositorAnimationHost();
+
+  return nullptr;
+}
+
 CompositorAnimationTimeline*
 PaintLayerScrollableArea::compositorAnimationTimeline() const {
-  if (LocalFrame* frame = box().frame()) {
-    if (Page* page = frame->page())
-      return page->scrollingCoordinator()
-                 ? page->scrollingCoordinator()->compositorAnimationTimeline()
-                 : nullptr;
-  }
+  if (ScrollingCoordinator* coordinator = getScrollingCoordinator())
+    return coordinator->compositorAnimationTimeline();
+
   return nullptr;
 }
 
 PaintLayerScrollableArea*
 PaintLayerScrollableArea::ScrollbarManager::scrollableArea() {
   return toPaintLayerScrollableArea(m_scrollableArea.get());
 }
 
 void PaintLayerScrollableArea::ScrollbarManager::destroyDetachedScrollbars() {
   DCHECK(!m_hBarIsAttached || m_hBar);
@@ skipping 199 matching lines @@
 
 void PaintLayerScrollableArea::DelayScrollOffsetClampScope::
     clampScrollableAreas() {
   for (auto& scrollableArea : *s_needsClamp)
     scrollableArea->clampScrollOffsetAfterOverflowChange();
   delete s_needsClamp;
   s_needsClamp = nullptr;
 }
 
 }  // namespace blink