Prevent recreation of UI resource holder when created with resource ID

cc/layers/ui_resource_layer.cc

 // Copyright 2013 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/layers/ui_resource_layer.h"
 
 #include "cc/layers/ui_resource_layer_impl.h"
 #include "cc/resources/prioritized_resource.h"
 #include "cc/resources/resource_update.h"
 #include "cc/resources/resource_update_queue.h"
 #include "cc/resources/scoped_ui_resource.h"
 #include "cc/resources/ui_resource_bitmap.h"
 #include "cc/trees/layer_tree_host.h"
 
 namespace cc {
 
 
 namespace {
 
 class ScopedUIResourceHolder : public UIResourceLayer::UIResourceHolder {
  public:
   static scoped_ptr<ScopedUIResourceHolder> Create(LayerTreeHost* host,
                                             const SkBitmap& skbitmap) {
     return make_scoped_ptr(new ScopedUIResourceHolder(host, skbitmap));
   }
   UIResourceId id() override { return resource_->id(); }
 
+  bool NeedsRecreation() override { return false; }
+
  private:
   ScopedUIResourceHolder(LayerTreeHost* host, const SkBitmap& skbitmap) {
     resource_ = ScopedUIResource::Create(host, UIResourceBitmap(skbitmap));
   }
 
   scoped_ptr<ScopedUIResource> resource_;
 };
 
 class SharedUIResourceHolder : public UIResourceLayer::UIResourceHolder {
  public:
-  static scoped_ptr<SharedUIResourceHolder> Create(UIResourceId id) {
-    return make_scoped_ptr(new SharedUIResourceHolder(id));
+  static scoped_ptr<SharedUIResourceHolder> Create(UIResourceId id,
+                                                   bool is_persistent) {
+    return make_scoped_ptr(new SharedUIResourceHolder(id, is_persistent));
   }
 
   UIResourceId id() override { return id_; }
 
+  bool NeedsRecreation() override { return !is_persistent_; }
+
  private:
-  explicit SharedUIResourceHolder(UIResourceId id) : id_(id) {}
+  SharedUIResourceHolder(UIResourceId id, bool is_persistent)
+      : id_(id), is_persistent_(is_persistent) {}
 
   UIResourceId id_;
+  bool is_persistent_;
 };
 
 }  // anonymous namespace
 
 UIResourceLayer::UIResourceHolder::~UIResourceHolder() {}
 
 scoped_refptr<UIResourceLayer> UIResourceLayer::Create() {
   return make_scoped_refptr(new UIResourceLayer());
 }
 
@@ skipping 47 matching lines @@
   if (host == layer_tree_host())
     return;
 
   Layer::SetLayerTreeHost(host);
 
   // Recreate the resource hold against the new LTH.
   RecreateUIResourceHolder();
 }
 
 void UIResourceLayer::RecreateUIResourceHolder() {
-  ui_resource_holder_ = nullptr;
   if (layer_tree_host() && !bitmap_.empty()) {
     ui_resource_holder_ =
         ScopedUIResourceHolder::Create(layer_tree_host(), bitmap_);
+  } else if (ui_resource_holder_ && !ui_resource_holder_->NeedsRecreation()) {
+    ui_resource_holder_ = nullptr;
   }
   UpdateDrawsContent(HasDrawableContent());
 }
 
 void UIResourceLayer::SetBitmap(const SkBitmap& skbitmap) {
   bitmap_ = skbitmap;
 
   RecreateUIResourceHolder();
   SetNeedsCommit();
 }
 
 void UIResourceLayer::SetUIResourceId(UIResourceId resource_id) {
+  SetUIResourceIdInternal(resource_id, false);
+}
+
+void UIResourceLayer::SetPersistentUIResourceId(UIResourceId resource_id) {
+  SetUIResourceIdInternal(resource_id, true);
+}
+
+void UIResourceLayer::SetUIResourceIdInternal(UIResourceId resource_id,
+                                              bool is_persistent) {
   if (ui_resource_holder_ && ui_resource_holder_->id() == resource_id)
     return;
 
   if (resource_id)
-    ui_resource_holder_ = SharedUIResourceHolder::Create(resource_id);
+    ui_resource_holder_ =
+        SharedUIResourceHolder::Create(resource_id, is_persistent);
   else
     ui_resource_holder_ = nullptr;
 
   UpdateDrawsContent(HasDrawableContent());
   SetNeedsCommit();
 }
 
 bool UIResourceLayer::HasDrawableContent() const {
   return ui_resource_holder_ && ui_resource_holder_->id() &&
          Layer::HasDrawableContent();
@@ skipping 11 matching lines @@
     gfx::Size image_size =
         layer_tree_host()->GetUIResourceSize(ui_resource_holder_->id());
     layer_impl->SetUIResourceId(ui_resource_holder_->id());
     layer_impl->SetImageBounds(image_size);
     layer_impl->SetUV(uv_top_left_, uv_bottom_right_);
     layer_impl->SetVertexOpacity(vertex_opacity_);
   }
 }
 
 }  // namespace cc