When possible, draw the toolbar shadow with the compositor

chrome/browser/android/compositor/layer/toolbar_layer.cc

Index: chrome/browser/android/compositor/layer/toolbar_layer.cc
diff --git a/chrome/browser/android/compositor/layer/toolbar_layer.cc b/chrome/browser/android/compositor/layer/toolbar_layer.cc
index a98ddbe59107ccfca56fcb40e6d2cfa9b5f45e77..1e4f411406200079206cd542e43c52746d2392b5 100644
--- a/chrome/browser/android/compositor/layer/toolbar_layer.cc
+++ b/chrome/browser/android/compositor/layer/toolbar_layer.cc
@@ -27,16 +27,20 @@ scoped_refptr<cc::Layer> ToolbarLayer::layer() {
 
 void ToolbarLayer::PushResource(
     int toolbar_resource_id,
+    int toolbar_shadow_resource_id,
     int toolbar_background_color,
     bool anonymize,
     int toolbar_textbox_background_color,
     int url_bar_background_resource_id,
     float url_bar_alpha,
     bool show_debug,
-    bool clip_shadow) {
+    bool show_shadow) {
   ui::ResourceManager::Resource* resource =
       resource_manager_->GetResource(ui::ANDROID_RESOURCE_TYPE_DYNAMIC,
                                      toolbar_resource_id);
+  ui::ResourceManager::Resource* shadow_resource =
+      resource_manager_->GetResource(ui::ANDROID_RESOURCE_TYPE_STATIC,
+                                     toolbar_shadow_resource_id);
 
   // Ensure the toolbar resource is available before making the layer visible.
   layer_->SetHideLayerAndSubtree(!resource);
@@ -87,7 +91,14 @@ void ToolbarLayer::PushResource(
   bitmap_layer_->SetUIResourceId(resource->ui_resource->id());
   bitmap_layer_->SetBounds(resource->size);
 
-  layer_->SetMasksToBounds(clip_shadow);
+  if (shadow_resource) {
+    toolbar_shadow_layer_->SetUIResourceId(shadow_resource->ui_resource->id());
+    toolbar_shadow_layer_->SetBounds(
+        gfx::Size(resource->size.width(), shadow_resource->size.height()));
+    toolbar_shadow_layer_->SetPosition(
+        gfx::PointF(0.0f, resource->padding.size().height()));
+    toolbar_shadow_layer_->SetHideLayerAndSubtree(!show_shadow);
+  }
 
   anonymize_layer_->SetHideLayerAndSubtree(!anonymize);
   if (anonymize) {
@@ -142,6 +153,7 @@ ToolbarLayer::ToolbarLayer(ui::ResourceManager* resource_manager)
     : resource_manager_(resource_manager),
       layer_(cc::Layer::Create()),
       toolbar_background_layer_(cc::SolidColorLayer::Create()),
+      toolbar_shadow_layer_(cc::UIResourceLayer::Create()),
       url_bar_background_layer_(cc::NinePatchLayer::Create()),
       bitmap_layer_(cc::UIResourceLayer::Create()),
       progress_bar_layer_(cc::SolidColorLayer::Create()),
@@ -151,6 +163,9 @@ ToolbarLayer::ToolbarLayer(ui::ResourceManager* resource_manager)
   toolbar_background_layer_->SetIsDrawable(true);
   layer_->AddChild(toolbar_background_layer_);
 
+  toolbar_shadow_layer_->SetIsDrawable(true);
+  layer_->AddChild(toolbar_shadow_layer_);
+
   url_bar_background_layer_->SetIsDrawable(true);
   url_bar_background_layer_->SetFillCenter(true);
   layer_->AddChild(url_bar_background_layer_);