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

cc/layer_tree_host.cc

Index: cc/layer_tree_host.cc
diff --git a/cc/layer_tree_host.cc b/cc/layer_tree_host.cc
index c4e8dd43c6925406fe7273923314edcd073609f1..658512e7b09ca05b6088a16c102a8e65d4166e1c 100644
--- a/cc/layer_tree_host.cc
+++ b/cc/layer_tree_host.cc
@@ -23,7 +23,11 @@
 #include "cc/math_util.h"
 #include "cc/occlusion_tracker.h"
 #include "cc/overdraw_metrics.h"
+#include "cc/pinch_zoom_scrollbar.h"
+#include "cc/pinch_zoom_scrollbar_geometry.h"
+#include "cc/pinch_zoom_scrollbar_painter.h"
 #include "cc/prioritized_resource_manager.h"
+#include "cc/scrollbar_layer.h"
 #include "cc/single_thread_proxy.h"
 #include "cc/switches.h"
 #include "cc/thread.h"
@@ -327,6 +331,13 @@ void LayerTreeHost::finishCommitOnImplThread(LayerTreeHostImpl* hostImpl)
             syncTree->ResetContentsTexturesPurged();
     }
 
+    syncTree->SetPinchZoomHorizontalLayerId(
+        m_pinchZoomScrollbarHorizontal ? m_pinchZoomScrollbarHorizontal->id() :
+                                         Layer::INVALID_ID);
+    syncTree->SetPinchZoomVerticalLayerId(
+        m_pinchZoomScrollbarVertical ? m_pinchZoomScrollbarVertical->id() :
+                                       Layer::INVALID_ID);
+
     if (!m_settings.implSidePainting) {
         // If we're not in impl-side painting, the tree is immediately
         // considered active.
@@ -339,9 +350,64 @@ void LayerTreeHost::finishCommitOnImplThread(LayerTreeHostImpl* hostImpl)
     m_commitNumber++;
 }
 
+void LayerTreeHost::setPinchZoomScrollbarsBoundsAndPosition()
+{
+    if (!m_pinchZoomScrollbarHorizontal || !m_pinchZoomScrollbarVertical)
+        return;
+
+    gfx::Size size = layoutViewportSize();
+    int trackWidth = PinchZoomScrollbarGeometry::kTrackWidth;
+
+    m_pinchZoomScrollbarHorizontal->SetBounds(gfx::Size(size.width() - trackWidth, trackWidth));
+    m_pinchZoomScrollbarHorizontal->SetPosition(gfx::PointF(0, size.height() - trackWidth));
+
+    m_pinchZoomScrollbarVertical->SetBounds(gfx::Size(trackWidth, size.height() - trackWidth));
+    m_pinchZoomScrollbarVertical->SetPosition(gfx::PointF(size.width() - trackWidth, 0));
+}
+
+static scoped_refptr<ScrollbarLayer> CreatePinchZoomScrollbar(
+    WebKit::WebScrollbar::Orientation orientation, LayerTreeHost* owner)
+{
+    scoped_refptr<ScrollbarLayer> scrollbarLayer = ScrollbarLayer::Create(
+        make_scoped_ptr(
+            new PinchZoomScrollbar(orientation, owner)).PassAs<WebKit::WebScrollbar>(),
+        scoped_ptr<ScrollbarThemePainter>(new PinchZoomScrollbarPainter).Pass(),
+        scoped_ptr<WebKit::WebScrollbarThemeGeometry>(
+            new PinchZoomScrollbarGeometry).Pass(),
+        Layer::PINCH_ZOOM_ROOT_SCROLL_LAYER_ID);
+    scrollbarLayer->SetIsDrawable(true);
+    scrollbarLayer->SetOpacity(0.f);
+    return scrollbarLayer;
+}
+
+void LayerTreeHost::createAndAddPinchZoomScrollbars()
+{
+    bool needsPropertiesUpdated = false;
+
+    if (!m_pinchZoomScrollbarHorizontal || !m_pinchZoomScrollbarVertical) {
+        m_pinchZoomScrollbarHorizontal = CreatePinchZoomScrollbar(WebKit::WebScrollbar::Horizontal, this);
+        m_pinchZoomScrollbarVertical = CreatePinchZoomScrollbar( WebKit::WebScrollbar::Vertical, this);
+        needsPropertiesUpdated = true;
+    }
+
+    DCHECK(m_pinchZoomScrollbarHorizontal && m_pinchZoomScrollbarVertical);
+
+    if (!m_pinchZoomScrollbarHorizontal->parent())
+        m_rootLayer->AddChild(m_pinchZoomScrollbarHorizontal);
+
+    if (!m_pinchZoomScrollbarVertical->parent())
+        m_rootLayer->AddChild(m_pinchZoomScrollbarVertical);
+
+    if (needsPropertiesUpdated)
+        setPinchZoomScrollbarsBoundsAndPosition();
+}
+
 void LayerTreeHost::willCommit()
 {
     m_client->willCommit();
+
+    if (m_settings.usePinchZoomScrollbars)
+        createAndAddPinchZoomScrollbars();
 }
 
 void LayerTreeHost::updateHudLayer()
@@ -480,6 +546,12 @@ void LayerTreeHost::setRootLayer(scoped_refptr<Layer> rootLayer)
     if (m_hudLayer)
         m_hudLayer->RemoveFromParent();
 
+    if (m_pinchZoomScrollbarHorizontal)
+        m_pinchZoomScrollbarHorizontal->RemoveFromParent();
+
+    if (m_pinchZoomScrollbarVertical)
+        m_pinchZoomScrollbarVertical->RemoveFromParent();
+
     setNeedsFullTreeSync();
 }
 
@@ -502,6 +574,7 @@ void LayerTreeHost::setViewportSize(const gfx::Size& layoutViewportSize, const g
     m_layoutViewportSize = layoutViewportSize;
     m_deviceViewportSize = deviceViewportSize;
 
+    setPinchZoomScrollbarsBoundsAndPosition();
     setNeedsCommit();
 }
 
@@ -595,6 +668,11 @@ static Layer* findFirstScrollableLayer(Layer* layer)
     return 0;
 }
 
+const Layer* LayerTreeHost::rootScrollLayer() const
+{
+    return findFirstScrollableLayer(m_rootLayer.get());
+}
+
 void LayerTreeHost::updateLayers(Layer* rootLayer, ResourceUpdateQueue& queue)
 {
     TRACE_EVENT0("cc", "LayerTreeHost::updateLayers");