Blink Support for Overlay Scrollbar Animation

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 aa12fe367fb90e3c05540f9a77bfcb9d33823948..9ebb13274c38d958afaa8914af56817d09611a08 100644
--- a/Source/platform/scroll/ScrollableArea.cpp
+++ b/Source/platform/scroll/ScrollableArea.cpp
@@ -34,13 +34,14 @@
 
 #include "platform/HostWindow.h"
 #include "platform/Logging.h"
+#include "platform/TraceEvent.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/geometry/FloatPoint.h"
 #include "platform/scroll/ProgrammaticScrollAnimator.h"
+#include "platform/scroll/ScrollbarStateTransitionAnimator.h"
 #include "platform/scroll/ScrollbarTheme.h"
 #include "wtf/PassOwnPtr.h"
 
-#include "platform/TraceEvent.h"
 
 static const int kPixelsPerLineStep = 40;
 static const float kMinFractionToStepWhenPaging = 0.875f;
@@ -109,6 +110,39 @@ ProgrammaticScrollAnimator* ScrollableArea::programmaticScrollAnimator() const
     return m_animators->programmaticScrollAnimator.get();
 }
 
+ScrollbarStateTransitionAnimator* ScrollableArea::scrollbarStateTransitionAnimator() const
+{
+    if (!m_animators)
+        m_animators = adoptPtr(new ScrollableAreaAnimators);
+
+    if (!m_animators->scrollbarStateTransitionAnimator)
+        m_animators->scrollbarStateTransitionAnimator = ScrollbarStateTransitionAnimator::create(const_cast<ScrollableArea*>(this));
+
+    return m_animators->scrollbarStateTransitionAnimator.get();
+}
+
+bool ScrollableArea::isDuringStateTransitionAnimation() const
+{
+    return hasOverlayScrollbars() && existingScrollbarStateTransitionAnimator() && existingScrollbarStateTransitionAnimator()->isDuringStateTransitionAnimation();
+}
+
+void ScrollableArea::stateTransitionInProgress()
+{
+    if (isDuringStateTransitionAnimation()) {
+        double progress = existingScrollbarStateTransitionAnimator()->stateTransitionProgress();
+        blink::WebThemeEngine::State startState = existingScrollbarStateTransitionAnimator()->stateTransitionStartState();
+        blink::WebThemeEngine::State endState = existingScrollbarStateTransitionAnimator()->stateTransitionEndState();
+
+        if (Scrollbar* verticalScrollbar = this->verticalScrollbar()) {
+            verticalScrollbar->updateStateTransitionData(startState, endState, progress);
+        }
+
+        if (Scrollbar* horizontalScrollbar = this->horizontalScrollbar()) {
+            horizontalScrollbar->updateStateTransitionData(startState, endState, progress);
+        }
+    }
+}
+
 void ScrollableArea::setScrollOrigin(const IntPoint& origin)
 {
     if (m_scrollOrigin != origin) {
@@ -301,11 +335,15 @@ void ScrollableArea::mouseMovedInContentArea() const
 void ScrollableArea::mouseEnteredScrollbar(Scrollbar* scrollbar) const
 {
     scrollAnimator()->mouseEnteredScrollbar(scrollbar);
+    if (ScrollbarStateTransitionAnimator* animator = scrollbarStateTransitionAnimator())
+        animator->mouseEnteredScrollbar(scrollbar);
 }
 
 void ScrollableArea::mouseExitedScrollbar(Scrollbar* scrollbar) const
 {
     scrollAnimator()->mouseExitedScrollbar(scrollbar);
+    if (ScrollbarStateTransitionAnimator* animator = scrollbarStateTransitionAnimator())
+        animator->mouseExitedScrollbar(scrollbar);
 }
 
 void ScrollableArea::contentAreaDidShow() const
@@ -442,6 +480,14 @@ void ScrollableArea::cancelProgrammaticScrollAnimation()
         programmaticScrollAnimator->cancelAnimation();
 }
 
+void ScrollableArea::serviceScrollbarAnimations()
+{
+    if (ScrollAnimator* scrollAnimator = existingScrollAnimator())
+        scrollAnimator->serviceScrollAnimations();
+    if (ScrollbarStateTransitionAnimator* animator = existingScrollbarStateTransitionAnimator())
+        animator->serviceAnimations();
+}
+
 IntRect ScrollableArea::visibleContentRect(IncludeScrollbarsInRect scrollbarInclusion) const
 {
     int verticalScrollbarWidth = 0;