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 cc08d55e19ad9c6f76a6fd9ab24871d61bd3e94d..dfc909a605a395a2bc79139b5d696d6e7ef63c7d 100644
--- a/cc/layer_tree_host.cc
+++ b/cc/layer_tree_host.cc
@@ -23,7 +23,10 @@
 #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_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"
@@ -332,6 +335,30 @@ void LayerTreeHost::finishCommitOnImplThread(LayerTreeHostImpl* hostImpl)
     m_commitNumber++;
 }
 
+void LayerTreeHost::setPinchZoomScrollbarPropertiesIfNeeded()
+{
+    gfx::Size size = layoutViewportSize();
+    int trackWidth = PinchZoomScrollbar::kTrackWidth;
+    Layer* rootScrollLayer = this->rootScrollLayer();
+    int rootScrollLayerId = rootScrollLayer ? rootScrollLayer->id() : 0;
+    if (m_pinchZoomScrollbarHorizontal) {
+        m_pinchZoomScrollbarHorizontal->setBounds(gfx::Size(size.width() - trackWidth, trackWidth));
+        m_pinchZoomScrollbarHorizontal->setPosition(gfx::PointF(0, size.height() - trackWidth));
+        m_pinchZoomScrollbarHorizontal->setIsDrawable(true);
+        m_pinchZoomScrollbarHorizontal->setOpacity(0.5);
+        m_pinchZoomScrollbarHorizontal->setNeedsDisplay();
+        m_pinchZoomScrollbarHorizontal->setScrollLayerId(rootScrollLayerId);
+    }
+    if (m_pinchZoomScrollbarVertical) {
+        m_pinchZoomScrollbarVertical->setBounds(gfx::Size(10, size.height() - 10));
+        m_pinchZoomScrollbarVertical->setPosition(gfx::PointF(size.width() - 10, 0));
+        m_pinchZoomScrollbarVertical->setIsDrawable(true);
+        m_pinchZoomScrollbarVertical->setOpacity(0.5);
+        m_pinchZoomScrollbarVertical->setNeedsDisplay();
+        m_pinchZoomScrollbarVertical->setScrollLayerId(rootScrollLayerId);
+    }
+}
+
 void LayerTreeHost::willCommit()
 {
     m_client->willCommit();
@@ -349,6 +376,36 @@ void LayerTreeHost::willCommit()
         m_hudLayer->removeFromParent();
         m_hudLayer = 0;
     }
+
+    // Setup pinch-zoom scrollbars if required.
+    if (m_settings.pageScalePinchZoomEnabled && rootScrollLayer() &&
+        !ScrollbarLayer::defaultUsesOverlayScrollbars()) {
+        if (!m_pinchZoomScrollbarHorizontal)
+            m_pinchZoomScrollbarHorizontal = ScrollbarLayer::create(
+                make_scoped_ptr(
+                    new PinchZoomScrollbar(
+                        WebKit::WebScrollbar::Horizontal, this)).PassAs<WebKit::WebScrollbar>(),
+                make_scoped_ptr(new PinchZoomScrollbarPainter).PassAs<ScrollbarThemePainter>(),
+                0);
+
+        DCHECK(m_pinchZoomScrollbarHorizontal);
+        if (!m_pinchZoomScrollbarHorizontal->parent())
+            m_rootLayer->addChild(m_pinchZoomScrollbarHorizontal);
+
+        if (!m_pinchZoomScrollbarVertical)
+            m_pinchZoomScrollbarVertical = ScrollbarLayer::create(
+                make_scoped_ptr(
+                    new PinchZoomScrollbar(
+                        WebKit::WebScrollbar::Vertical, this)).PassAs<WebKit::WebScrollbar>(),
+                make_scoped_ptr(new PinchZoomScrollbarPainter).PassAs<ScrollbarThemePainter>(),
+                0);
+
+       DCHECK(m_pinchZoomScrollbarVertical);
+       if (!m_pinchZoomScrollbarVertical->parent())
+            m_rootLayer->addChild(m_pinchZoomScrollbarVertical);
+
+       setPinchZoomScrollbarPropertiesIfNeeded();
+    }
 }
 
 void LayerTreeHost::commitComplete()
@@ -491,6 +548,7 @@ void LayerTreeHost::setViewportSize(const gfx::Size& layoutViewportSize, const g
     m_layoutViewportSize = layoutViewportSize;
     m_deviceViewportSize = deviceViewportSize;
 
+    setPinchZoomScrollbarPropertiesIfNeeded();
     setNeedsCommit();
 }
 
@@ -584,6 +642,11 @@ static Layer* findFirstScrollableLayer(Layer* layer)
     return 0;
 }
 
+Layer* LayerTreeHost::rootScrollLayer() const
+{
+    return findFirstScrollableLayer(m_rootLayer.get());
+}
+
 void LayerTreeHost::updateLayers(Layer* rootLayer, ResourceUpdateQueue& queue)
 {
     TRACE_EVENT0("cc", "LayerTreeHost::updateLayers");