Create Pinch Virtual Viewport scrollbar layers in Blink.

Source/web/WebViewImpl.cpp

 /*
  * Copyright (C) 2011, 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 137 matching lines @@
 #include "core/platform/graphics/ColorSpace.h"
 #include "core/platform/graphics/Extensions3D.h"
 #include "core/platform/graphics/FontCache.h"
 #include "core/platform/graphics/FontDescription.h"
 #include "core/platform/graphics/GraphicsContext.h"
 #include "core/platform/graphics/GraphicsContext3D.h"
 #include "core/platform/graphics/Image.h"
 #include "core/platform/graphics/ImageBuffer.h"
 #include "core/platform/graphics/chromium/LayerPainterChromium.h"
 #include "core/platform/graphics/gpu/SharedGraphicsContext3D.h"
+#include "core/rendering/RenderLayerCompositor.h"
 #include "core/rendering/RenderView.h"
 #include "core/rendering/RenderWidget.h"
 #include "core/rendering/TextAutosizer.h"
 #include "modules/geolocation/GeolocationController.h"
 #include "weborigin/SchemeRegistry.h"
 #include "weborigin/SecurityOrigin.h"
 #include "weborigin/SecurityPolicy.h"
 #include "painting/ContinuousPainter.h"
 
 #if ENABLE(DEFAULT_RENDER_THEME)
@@ skipping 3628 matching lines @@
 
     if (page()->settings().pinchVirtualViewportEnabled()) {
         if (!m_pinchViewports)
             m_pinchViewports = PinchViewports::create(this);
 
         m_pinchViewports->setOverflowControlsHostLayer(layer);
         m_pinchViewports->setViewportSize(mainFrameImpl()->frame()->view()->frameRect().size());
         if (layer) {
             m_rootGraphicsLayer = m_pinchViewports->rootGraphicsLayer();
             m_rootLayer = m_pinchViewports->rootGraphicsLayer()->platformLayer();
-            m_pinchViewports->registerViewportLayersWithTreeView(m_layerTreeView);
         } else {
             m_rootGraphicsLayer = 0;
             m_rootLayer = 0;
-            m_pinchViewports->clearViewportLayersForTreeView(m_layerTreeView);
         }
     } else {
         m_rootGraphicsLayer = layer;
         m_rootLayer = layer ? layer->platformLayer() : 0;
     }
 
     setIsAcceleratedCompositingActive(layer);
 
     if (m_layerTreeView) {
-        if (m_rootLayer)
+        if (m_rootLayer) {
             m_layerTreeView->setRootLayer(*m_rootLayer);
-        else
+            // We register viewport layers here since there may not be a layer
+            // tree view prior to this point.
+            if (m_pinchViewports) {
+                m_pinchViewports->registerViewportLayersWithTreeView(m_layerTreeView);
+            } else {
+                GraphicsLayer* rootScrollLayer = compositor()->scrollLayer();
+                m_layerTreeView->registerViewportLayers(m_rootLayer, rootScrollLayer->platformLayer(), 0);
+            }
+        } else {
             m_layerTreeView->clearRootLayer();
+            if (m_pinchViewports)
+                m_pinchViewports->clearViewportLayersForTreeView(m_layerTreeView);
+            else
+                m_layerTreeView->clearViewportLayers();
+        }
     }
 
     suppressInvalidations(false);
 }
 
 void WebViewImpl::scheduleCompositingLayerSync()
 {
     m_layerTreeView->setNeedsRedraw();
 }
 
@@ skipping 279 matching lines @@
     //    the initial viewport width.
     // 2. The author has disabled viewport zoom.
 
     const PageScaleConstraints& constraints = m_pageScaleConstraintsSet.pageDefinedConstraints();
 
     return fixedLayoutSize().width == m_size.width
         || (constraints.minimumScale == constraints.maximumScale && constraints.minimumScale != -1);
 }
 
 } // namespace WebKit