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 fbd6e6ac14d03fae7346f95edaab1614b976cbaf..f77e806bf37e67843c39e133e790a479184380fa 100644
--- a/cc/layer_tree_host.cc
+++ b/cc/layer_tree_host.cc
@@ -21,6 +21,8 @@
 #include "cc/math_util.h"
 #include "cc/occlusion_tracker.h"
 #include "cc/overdraw_metrics.h"
+#include "cc/pinch_zoom_scrollbar_layer.h"
+#include "cc/scrollbar_layer_impl.h"
 #include "cc/single_thread_proxy.h"
 #include "cc/switches.h"
 #include "cc/thread.h"
@@ -92,6 +94,11 @@ LayerTreeHost::LayerTreeHost(LayerTreeHostClient* client, const LayerTreeSetting
     , m_partialTextureUpdateRequests(0)
 {
     numLayerTreeInstances++;
+
+    if (m_settings.pageScalePinchZoomEnabled) {
+        m_pinchZoomScrollbarVertical = PinchZoomScrollbarLayer::create();
+        m_pinchZoomScrollbarHorizontal = PinchZoomScrollbarLayer::create();
+    }
 }
 
 bool LayerTreeHost::initialize(scoped_ptr<Thread> implThread)
@@ -280,6 +287,16 @@ void LayerTreeHost::finishCommitOnImplThread(LayerTreeHostImpl* hostImpl)
     else
         hostImpl->activeTree()->set_hud_layer(0);
 
+    if (m_rootLayer && m_pinchZoomScrollbarVertical)
+        hostImpl->activeTree()->set_pinch_zoom_scrollbar_vertical(static_cast<ScrollbarLayerImpl*>(LayerTreeHostCommon::findLayerInSubtree(hostImpl->rootLayer(), m_pinchZoomScrollbarVertical->id())));
+    else
+        hostImpl->activeTree()->set_pinch_zoom_scrollbar_vertical(0);
+
+    if (m_rootLayer && m_pinchZoomScrollbarHorizontal)
+        hostImpl->activeTree()->set_pinch_zoom_scrollbar_horizontal(static_cast<ScrollbarLayerImpl*>(LayerTreeHostCommon::findLayerInSubtree(hostImpl->rootLayer(), m_pinchZoomScrollbarHorizontal->id())));
+    else
+        hostImpl->activeTree()->set_pinch_zoom_scrollbar_horizontal(0);
+
     // We may have added an animation during the tree sync. This will cause both layer tree hosts
     // to visit their controllers.
     if (rootLayer() && m_needsAnimateLayers)
@@ -313,6 +330,16 @@ void LayerTreeHost::willCommit()
         m_hudLayer->removeFromParent();
         m_hudLayer = 0;
     }
+
+    if (m_settings.pageScalePinchZoomEnabled && m_rootLayer) {
+        DCHECK(m_pinchZoomScrollbarVertical);
+        if (m_pinchZoomScrollbarVertical && !m_pinchZoomScrollbarVertical->parent())
+            m_rootLayer->addChild(m_pinchZoomScrollbarVertical);
+
+        DCHECK(m_pinchZoomScrollbarHorizontal);
+        if (m_pinchZoomScrollbarHorizontal && !m_pinchZoomScrollbarHorizontal->parent())
+            m_rootLayer->addChild(m_pinchZoomScrollbarHorizontal);
+    }
 }
 
 void LayerTreeHost::commitComplete()
@@ -438,6 +465,12 @@ void LayerTreeHost::setRootLayer(scoped_refptr<Layer> rootLayer)
     if (m_hudLayer)
         m_hudLayer->removeFromParent();
 
+    if (m_pinchZoomScrollbarVertical)
+        m_pinchZoomScrollbarVertical->removeFromParent();
+
+    if (m_pinchZoomScrollbarHorizontal)
+        m_pinchZoomScrollbarHorizontal->removeFromParent();
+
     setNeedsFullTreeSync();
 }
 
@@ -568,9 +601,13 @@ void LayerTreeHost::updateLayers(Layer* rootLayer, ResourceUpdateQueue& queue)
 
     {
         if (m_settings.pageScalePinchZoomEnabled) {
-            Layer* rootScroll = findFirstScrollableLayer(rootLayer);
-            if (rootScroll)
-                rootScroll->setImplTransform(m_implTransform);
+            const LayerList& children = m_rootLayer->children();
+            for (size_t i = 0; i < children.size(); ++i) {
+                Layer* layer = children[i].get();
+                if (layer != m_pinchZoomScrollbarVertical.get()
+                    && layer != m_pinchZoomScrollbarHorizontal.get())
+                layer->setImplTransform(m_implTransform);
+            }
         }
 
         TRACE_EVENT0("cc", "LayerTreeHost::updateLayers::calcDrawEtc");