Implement pinch-zoom scaling for main-frame scrollbars and pinch-zoom overlay scrollbars.

cc/layer_tree_host_impl.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/layer_tree_host_impl.h"
 
 #include <algorithm>
 
 #include "base/basictypes.h"
 #include "base/debug/trace_event.h"
@@ skipping 1186 matching lines @@
     // in the most recent frame.
     LayerImpl* layerImpl = LayerTreeHostCommon::findLayerThatIsHitByPoint(deviceViewportPoint, activeTree()->RenderSurfaceLayerList());
 
     // Walk up the hierarchy and look for a scrollable layer.
     LayerImpl* potentiallyScrollingLayerImpl = 0;
     for (; layerImpl; layerImpl = layerImpl->parent()) {
         // The content layer can also block attempts to scroll outside the main thread.
         if (layerImpl->TryScroll(deviceViewportPoint, type) == ScrollOnMainThread) {
             m_numMainThreadScrolls++;
             UMA_HISTOGRAM_BOOLEAN("TryScroll.SlowScroll", true);
+            activeTree()->DidBeginScroll();
             return ScrollOnMainThread;
         }
 
         LayerImpl* scrollLayerImpl = findScrollLayerForContentLayer(layerImpl);
         if (!scrollLayerImpl)
             continue;
 
         ScrollStatus status = scrollLayerImpl->TryScroll(deviceViewportPoint, type);
 
         // If any layer wants to divert the scroll event to the main thread, abort.
         if (status == ScrollOnMainThread) {
             m_numMainThreadScrolls++;
             UMA_HISTOGRAM_BOOLEAN("TryScroll.SlowScroll", true);
+            activeTree()->DidBeginScroll();
             return ScrollOnMainThread;
         }
 
         if (status == ScrollStarted && !potentiallyScrollingLayerImpl)
             potentiallyScrollingLayerImpl = scrollLayerImpl;
     }
 
     // When hiding top controls is enabled and the controls are hidden or
     // overlaying the content, force scrolls to be enabled on the root layer to
     // allow bringing the top controls back into view.
     if (!potentiallyScrollingLayerImpl && m_topControlsManager &&
             m_topControlsManager->content_top_offset() != m_settings.topControlsHeight) {
         potentiallyScrollingLayerImpl = rootScrollLayer();
     }
 
     if (potentiallyScrollingLayerImpl) {
         m_activeTree->set_currently_scrolling_layer(potentiallyScrollingLayerImpl);
         m_shouldBubbleScrolls = (type != NonBubblingGesture);
         m_wheelScrolling = (type == Wheel);
         m_numImplThreadScrolls++;
         m_client->renewTreePriority();
         UMA_HISTOGRAM_BOOLEAN("TryScroll.SlowScroll", false);
+        activeTree()->DidBeginScroll();
         return ScrollStarted;
     }
     return ScrollIgnored;
 }
 
 gfx::Vector2dF LayerTreeHostImpl::scrollLayerWithViewportSpaceDelta(LayerImpl* layerImpl, float scaleFromViewportToScreenSpace, gfx::PointF viewportPoint, gfx::Vector2dF viewportDelta)
 {
     // Layers with non-invertible screen space transforms should not have passed the scroll hit
     // test in the first place.
     DCHECK(layerImpl->screen_space_transform().IsInvertible());
@@ skipping 103 matching lines @@
 
         // Allow further movement only on an axis perpendicular to the direction in which the layer
         // moved.
         gfx::Vector2dF perpendicularAxis(-appliedDelta.y(), appliedDelta.x());
         pendingDelta = MathUtil::projectVector(pendingDelta, perpendicularAxis);
 
         if (gfx::ToFlooredVector2d(pendingDelta).IsZero())
             break;
     }
 
+    activeTree()->DidUpdateScroll();
     if (didScroll) {
         m_client->setNeedsCommitOnImplThread();
         m_client->setNeedsRedrawOnImplThread();
         m_client->renewTreePriority();
     }
     return didScroll;
 }
 
 void LayerTreeHostImpl::clearCurrentlyScrollingLayer()
 {
     m_activeTree->ClearCurrentlyScrollingLayer();
     m_didLockScrollingLayer = false;
 }
 
 void LayerTreeHostImpl::scrollEnd()
 {
     if (m_topControlsManager)
         m_topControlsManager->ScrollEnd();
     clearCurrentlyScrollingLayer();
+    activeTree()->DidEndScroll();
 }
 
 void LayerTreeHostImpl::pinchGestureBegin()
 {
     m_pinchGestureActive = true;
     m_previousPinchAnchor = gfx::Point();
     m_client->renewTreePriority();
 }
 
 void LayerTreeHostImpl::pinchGestureUpdate(float magnifyDelta, gfx::Point anchor)
@@ skipping 337 matching lines @@
         m_tileManager->SetRecordRenderingStats(m_debugState.recordRenderingStats());
 }
 
 void LayerTreeHostImpl::savePaintTime(const base::TimeDelta& totalPaintTime, int commitNumber)
 {
     DCHECK(m_debugState.continuousPainting);
     m_paintTimeCounter->SavePaintTime(totalPaintTime, commitNumber);
 }
 
 }  // namespace cc