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

cc/scrollbar_layer_impl.cc

 // Copyright 2012 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/scrollbar_layer_impl.h"
 
 #include "cc/layer_tree_impl.h"
 #include "cc/quad_sink.h"
 #include "cc/scrollbar_animation_controller.h"
 #include "cc/texture_draw_quad.h"
@@ skipping 23 matching lines @@
     , m_scrollbarOverlayStyle(WebScrollbar::ScrollbarOverlayStyleDefault)
     , m_orientation(WebScrollbar::Horizontal)
     , m_controlSize(WebScrollbar::RegularScrollbar)
     , m_pressedPart(WebScrollbar::NoPart)
     , m_hoveredPart(WebScrollbar::NoPart)
     , m_isScrollableAreaActive(false)
     , m_isScrollViewScrollbar(false)
     , m_enabled(false)
     , m_isCustomScrollbar(false)
     , m_isOverlayScrollbar(false)
+    , m_isPinchZoomScrollbar(false)
 {
 }
 
 ScrollbarLayerImpl::~ScrollbarLayerImpl()
 {
 }
 
 ScrollbarLayerImpl* ScrollbarLayerImpl::toScrollbarLayer()
 {
     return this;
@@ skipping 75 matching lines @@
     scrollbarLayer->setScrollbarData(&m_scrollbar);
     scrollbarLayer->setThumbSize(m_thumbSize);
 
     scrollbarLayer->setBackTrackResourceId(m_backTrackResourceId);
     scrollbarLayer->setForeTrackResourceId(m_foreTrackResourceId);
     scrollbarLayer->setThumbResourceId(m_thumbResourceId);
 }
 
 void ScrollbarLayerImpl::appendQuads(QuadSink& quadSink, AppendQuadsData& appendQuadsData)
 {
+    if (isPinchZoomScrollbar()) {
+        LayerImpl* rootScrollLayer = layerTreeImpl()->RootScrollLayer();
+        LayerImpl* currentlyScrollingLayer = layerTreeImpl()->CurrentlyScrollingLayer();
+        bool pinchZoomScrollbarShouldDraw = rootScrollLayer &&
+                                            rootScrollLayer == currentlyScrollingLayer &&
+                                            layerTreeImpl()->total_page_scale_factor() > 1;
+        if (!pinchZoomScrollbarShouldDraw)
+            return;
+    }
+
     bool premultipledAlpha = false;
     bool flipped = false;
     gfx::PointF uvTopLeft(0.f, 0.f);
     gfx::PointF uvBottomRight(1.f, 1.f);
     gfx::Rect boundsRect(gfx::Point(), bounds());
     gfx::Rect contentBoundsRect(gfx::Point(), contentBounds());
 
     SharedQuadState* sharedQuadState = quadSink.useSharedQuadState(createSharedQuadState());
     appendDebugBorderQuad(quadSink, sharedQuadState, appendQuadsData);
 
@@ skipping 123 matching lines @@
 {
     return m_owner->m_isCustomScrollbar;
 }
 
 const char* ScrollbarLayerImpl::layerTypeAsString() const
 {
     return "ScrollbarLayer";
 }
 
 }  // namespace cc