Make ViewportScrollCallback an interface and add child and root classes

third_party/WebKit/Source/core/page/scrolling/ViewportScrollCallback.cpp

Index: third_party/WebKit/Source/core/page/scrolling/ViewportScrollCallback.cpp
diff --git a/third_party/WebKit/Source/core/page/scrolling/ViewportScrollCallback.cpp b/third_party/WebKit/Source/core/page/scrolling/ViewportScrollCallback.cpp
index f8cc13a7ff8d3c9b0a824568832561bc51bfe749..0c0e1d835db0954928d3ae657f22578fad853703 100644
--- a/third_party/WebKit/Source/core/page/scrolling/ViewportScrollCallback.cpp
+++ b/third_party/WebKit/Source/core/page/scrolling/ViewportScrollCallback.cpp
@@ -4,101 +4,28 @@
 
 #include "core/page/scrolling/ViewportScrollCallback.h"
 
-#include "core/frame/FrameHost.h"
-#include "core/frame/FrameView.h"
-#include "core/frame/Settings.h"
-#include "core/frame/TopControls.h"
-#include "core/page/scrolling/OverscrollController.h"
 #include "core/page/scrolling/ScrollState.h"
-#include "platform/geometry/FloatSize.h"
 #include "platform/scroll/ScrollableArea.h"
 
 namespace blink {
 
-ViewportScrollCallback::ViewportScrollCallback(
-    TopControls* topControls, OverscrollController* overscrollController)
-    : m_topControls(topControls)
-    , m_overscrollController(overscrollController)
+ScrollResult ViewportScrollCallback::performNativeScroll(
+    ScrollState& state, ScrollableArea& scroller)
 {
-}
-
-ViewportScrollCallback::~ViewportScrollCallback()
-{
-}
-
-DEFINE_TRACE(ViewportScrollCallback)
-{
-    visitor->trace(m_topControls);
-    visitor->trace(m_overscrollController);
-    visitor->trace(m_scroller);
-    ScrollStateCallback::trace(visitor);
-}
-
-bool ViewportScrollCallback::shouldScrollTopControls(const FloatSize& delta,
-    ScrollGranularity granularity) const
-{
-    if (granularity != ScrollByPixel && granularity != ScrollByPrecisePixel)
-        return false;
-
-    if (!m_scroller)
-        return false;
-
-    DoublePoint maxScroll = m_scroller->maximumScrollPositionDouble();
-    DoublePoint scrollPosition = m_scroller->scrollPositionDouble();
-
-    // Always give the delta to the top controls if the scroll is in
-    // the direction to show the top controls. If it's in the
-    // direction to hide the top controls, only give the delta to the
-    // top controls when the frame can scroll.
-    return delta.height() < 0 || scrollPosition.y() < maxScroll.y();
-}
-
-void ViewportScrollCallback::handleEvent(ScrollState* state)
-{
-    FloatSize delta(state->deltaX(), state->deltaY());
+    FloatSize delta(state.deltaX(), state.deltaY());
     ScrollGranularity granularity =
-        ScrollGranularity(static_cast<int>(state->deltaGranularity()));
-    FloatSize remainingDelta = delta;
-
-    // Scroll top controls.
-    if (m_topControls) {
-        if (state->isBeginning())
-            m_topControls->scrollBegin();
-
-        if (shouldScrollTopControls(delta, granularity))
-            remainingDelta = m_topControls->scrollBy(delta);
-    }
-
-    bool topControlsConsumedScroll = remainingDelta.height() != delta.height();
+        ScrollGranularity(static_cast<int>(state.deltaGranularity()));
 
-    // Scroll the element's scrollable area.
-    if (!m_scroller)
-        return;
-
-    ScrollResult result = m_scroller->userScroll(granularity, remainingDelta);
-
-    // We consider top controls movement to be scrolling.
-    result.didScrollY |= topControlsConsumedScroll;
-
-    // Handle Overscroll.
-    if (m_overscrollController) {
-        FloatPoint position(state->positionX(), state->positionY());
-        FloatSize velocity(state->velocityX(), state->velocityY());
-        m_overscrollController->handleOverscroll(result, position, velocity);
-    }
+    ScrollResult result = scroller.userScroll(granularity, delta);
 
     // The viewport consumes everything.
     // TODO(bokan): This isn't actually consuming everything but doing so breaks
-    // the main thread pull-to-refresh action. I need to figure out where that
-    // gets activated. crbug.com/607210.
-    state->consumeDeltaNative(
-        state->deltaX() - result.unusedScrollDeltaX,
-        state->deltaY() - result.unusedScrollDeltaY);
-}
+    // the main thread pull-to-refresh action. crbug.com/607210.
+    state.consumeDeltaNative(
+        delta.width() - result.unusedScrollDeltaX,
+        delta.height() - result.unusedScrollDeltaY);
 
-void ViewportScrollCallback::setScroller(ScrollableArea* scroller)
-{
-    m_scroller = scroller;
+    return result;
 }
 
 } // namespace blink