Implement CSSOM Smooth Scroll API

Source/platform/scroll/ScrollableArea.cpp

Index: Source/platform/scroll/ScrollableArea.cpp
diff --git a/Source/platform/scroll/ScrollableArea.cpp b/Source/platform/scroll/ScrollableArea.cpp
index b6dbd83c7e23446ba60408c856327903527c829c..dcc8c489d4b79baf65090a82ab35abc8053ee6eb 100644
--- a/Source/platform/scroll/ScrollableArea.cpp
+++ b/Source/platform/scroll/ScrollableArea.cpp
@@ -34,6 +34,7 @@
 
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/geometry/FloatPoint.h"
+#include "platform/scroll/ProgrammaticScrollAnimator.h"
 #include "platform/scroll/ScrollbarTheme.h"
 #include "wtf/PassOwnPtr.h"
 
@@ -48,7 +49,7 @@ struct SameSizeAsScrollableArea {
     virtual ~SameSizeAsScrollableArea();
     unsigned damageBits : 2;
     IntRect scrollbarDamage[2];
-    void* pointer;
+    void* pointer[2];
     unsigned bitfields : 16;
     IntPoint origin;
 };
@@ -95,6 +96,14 @@ ScrollAnimator* ScrollableArea::scrollAnimator() const
     return m_scrollAnimator.get();
 }
 
+ProgrammaticScrollAnimator* ScrollableArea::programmaticScrollAnimator() const
+{
+    if (!m_programmaticScrollAnimator)
+        m_programmaticScrollAnimator = ProgrammaticScrollAnimator::create(const_cast<ScrollableArea*>(this));
+
+    return m_programmaticScrollAnimator.get();
+}
+
 void ScrollableArea::setScrollOrigin(const IntPoint& origin)
 {
     if (m_scrollOrigin != origin) {
@@ -120,6 +129,8 @@ bool ScrollableArea::scroll(ScrollDirection direction, ScrollGranularity granula
     if (!userInputScrollable(orientation))
         return false;
 
+    cancelProgrammaticScrollAnimation();
+
     float step = 0;
     switch (granularity) {
     case ScrollByLine:
@@ -145,6 +156,7 @@ bool ScrollableArea::scroll(ScrollDirection direction, ScrollGranularity granula
 
 void ScrollableArea::scrollToOffsetWithoutAnimation(const FloatPoint& offset)
 {
+    cancelProgrammaticScrollAnimation();
     scrollAnimator()->scrollToOffsetWithoutAnimation(offset);
 }
 
@@ -156,6 +168,14 @@ void ScrollableArea::scrollToOffsetWithoutAnimation(ScrollbarOrientation orienta
         scrollToOffsetWithoutAnimation(FloatPoint(scrollAnimator()->currentPosition().x(), offset));
 }
 
+void ScrollableArea::programmaticallyScrollSmoothlyToOffset(const FloatPoint& offset)
+{
+    if (ScrollAnimator* scrollAnimator = existingScrollAnimator())
+        scrollAnimator->cancelAnimations();
+    cancelProgrammaticScrollAnimation();
+    programmaticScrollAnimator()->animateToOffset(offset);
+}
+
 void ScrollableArea::notifyScrollPositionChanged(const IntPoint& position)
 {
     scrollPositionChanged(position);
@@ -217,6 +237,7 @@ bool ScrollableArea::handleWheelEvent(const PlatformWheelEvent& wheelEvent)
     if (wheelEvent.modifiers() & PlatformEvent::CtrlKey)
         return false;
 
+    cancelProgrammaticScrollAnimation();
     return scrollAnimator()->handleWheelEvent(wheelEvent);
 }
 
@@ -392,10 +413,45 @@ bool ScrollableArea::hasLayerForScrollCorner() const
     return layerForScrollCorner();
 }
 
-void ScrollableArea::serviceScrollAnimations()
+void ScrollableArea::serviceScrollAnimations(double monotonicTime)
 {
     if (ScrollAnimator* scrollAnimator = existingScrollAnimator())
         scrollAnimator->serviceScrollAnimations();
+    if (ProgrammaticScrollAnimator* programmaticScrollAnimator = existingProgrammaticScrollAnimator())
+        programmaticScrollAnimator->tickAnimation(monotonicTime);
+}
+
+void ScrollableArea::notifyAnimationStarted(double monotonicTime)
+{
+    programmaticScrollAnimator()->notifyAnimationStarted(monotonicTime);
+}
+
+void ScrollableArea::notifyAnimationFinished(double monotonicTime)
+{
+    programmaticScrollAnimator()->notifyAnimationFinished(monotonicTime);
+}
+
+void ScrollableArea::layerForScrollingDidChange()
+{
+    if (ProgrammaticScrollAnimator* programmaticScrollAnimator = existingProgrammaticScrollAnimator())
+        programmaticScrollAnimator->canUseCompositedScrollAnimationsDidChange();
+}
+
+void ScrollableArea::requiresMainThreadScrollingDidChange()
+{
+    if (ProgrammaticScrollAnimator* programmaticScrollAnimator = existingProgrammaticScrollAnimator())
+        programmaticScrollAnimator->canUseCompositedScrollAnimationsDidChange();
+}
+
+bool ScrollableArea::canUseCompositedScrollAnimations() const
+{
+    return layerForScrolling() && !layerForScrolling()->platformLayer()->shouldScrollOnMainThread();
+}
+
+void ScrollableArea::cancelProgrammaticScrollAnimation()
+{
+    if (ProgrammaticScrollAnimator* programmaticScrollAnimator = existingProgrammaticScrollAnimator())
+        programmaticScrollAnimator->cancelAnimation();
 }
 
 IntRect ScrollableArea::visibleContentRect(IncludeScrollbarsInRect scrollbarInclusion) const