cc: Only allow trees created at the current viewport size to draw.

cc/layer_tree_impl.cc

 // Copyright 2011 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/layer_tree_impl.h"
 
 #include "base/debug/trace_event.h"
 #include "cc/heads_up_display_layer_impl.h"
 #include "cc/layer_tree_host_common.h"
 #include "cc/layer_tree_host_impl.h"
@@ skipping 74 matching lines @@
   set_needs_update_draw_properties();
   return root_layer_.Pass();
 }
 
 void LayerTreeImpl::pushPropertiesTo(LayerTreeImpl* target_tree) {
   target_tree->SetPageScaleFactorAndLimits(
       page_scale_factor(), min_page_scale_factor(), max_page_scale_factor());
   target_tree->SetPageScaleDelta(
       target_tree->page_scale_delta() / target_tree->sent_page_scale_delta());
   target_tree->set_sent_page_scale_delta(1);
+  target_tree->SetViewportSize(layout_viewport_size_, device_viewport_size_);
 
   // This should match the property synchronization in
   // LayerTreeHost::finishCommitOnImplThread().
   target_tree->set_source_frame_number(source_frame_number());
   target_tree->set_background_color(background_color());
   target_tree->set_has_transparent_background(has_transparent_background());
 
   if (ContentsTexturesPurged())
     target_tree->SetContentsTexturesPurged();
   else
@@ skipping 157 matching lines @@
         ClearRenderSurfacesOnLayerImplRecursive(current->children()[i]);
     current->clearRenderSurface();
 }
 
 void LayerTreeImpl::ClearRenderSurfaces() {
   ClearRenderSurfacesOnLayerImplRecursive(RootLayer());
   render_surface_layer_list_.clear();
   set_needs_update_draw_properties();
 }
 
+void LayerTreeImpl::SetViewportSize(gfx::Size layout_viewport_size,
+                                    gfx::Size device_viewport_size) {
+    if (device_viewport_size_ == device_viewport_size &&

[danakj, 2013/02/13 08:19:54]

sorry, but 2 space indent here :|

+        layout_viewport_size_ == layout_viewport_size)
+        return;
+
+    layout_viewport_size_ = layout_viewport_size;
+    device_viewport_size_ = device_viewport_size;
+
+    UpdateMaxScrollOffset();
+
+    if (IsActiveTree() && layer_tree_host_impl_->renderer())
+        layer_tree_host_impl_->renderer()->viewportChanged();
+
+    layer_tree_host_impl_->OnCanDrawStateChangedForTree(this);
+}
+
 bool LayerTreeImpl::AreVisibleResourcesReady() const {
   TRACE_EVENT0("cc", "LayerTreeImpl::AreVisibleResourcesReady");
 
   typedef LayerIterator<LayerImpl,
                         std::vector<LayerImpl*>,
                         RenderSurfaceImpl,
                         LayerIteratorActions::BackToFront> LayerIteratorType;
   LayerIteratorType end = LayerIteratorType::end(&render_surface_layer_list_);
   for (LayerIteratorType it = LayerIteratorType::begin(
            &render_surface_layer_list_); it != end; ++it) {
@@ skipping 139 matching lines @@
 }
 
 const LayerTreeDebugState& LayerTreeImpl::debug_state() const {
   return layer_tree_host_impl_->debugState();
 }
 
 float LayerTreeImpl::device_scale_factor() const {
   return layer_tree_host_impl_->deviceScaleFactor();
 }
 
-const gfx::Size& LayerTreeImpl::device_viewport_size() const {
-  return layer_tree_host_impl_->deviceViewportSize();
-}
-
-const gfx::Size& LayerTreeImpl::layout_viewport_size() const {
-  return layer_tree_host_impl_->layoutViewportSize();
-}
-
 std::string LayerTreeImpl::layer_tree_as_text() const {
   return layer_tree_host_impl_->layerTreeAsText();
 }
 
 DebugRectHistory* LayerTreeImpl::debug_rect_history() const {
   return layer_tree_host_impl_->debugRectHistory();
 }
 
 AnimationRegistrar* LayerTreeImpl::animationRegistrar() const {
   return layer_tree_host_impl_->animationRegistrar();
 }
 
 } // namespace cc