Use std::unique_ptr to signal ownership transfer in WebCompositorSupport

third_party/WebKit/public/platform/WebCompositorSupport.h

 /*
  * Copyright (C) 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 14 matching lines @@
 
 #ifndef WebCompositorSupport_h
 #define WebCompositorSupport_h
 
 #include "WebCommon.h"
 #include "WebFloatPoint.h"
 #include "WebLayerTreeView.h"
 #include "WebScrollbar.h"
 #include "WebScrollbarThemePainter.h"
 
+#include <memory>
+
 namespace cc {
 class Layer;
 class TextureLayerClient;
 }
 
 namespace blink {
 
 class WebContentLayer;
 class WebContentLayerClient;
 class WebExternalTextureLayer;
 class WebImageLayer;
 class WebLayer;
 class WebScrollbarLayer;
 class WebScrollbarThemeGeometry;
 
 class WebCompositorSupport {
  public:
   // Layers -------------------------------------------------------
 
-  virtual WebLayer* createLayer() { return nullptr; }
+  virtual std::unique_ptr<WebLayer> createLayer() = 0;
 
-  virtual WebLayer* createLayerFromCCLayer(cc::Layer*) { return nullptr; }
+  virtual std::unique_ptr<WebLayer> createLayerFromCCLayer(cc::Layer*) = 0;
 
-  virtual WebContentLayer* createContentLayer(WebContentLayerClient*) {
-    return nullptr;
-  }
+  virtual std::unique_ptr<WebContentLayer> createContentLayer(
+      WebContentLayerClient*) = 0;
 
-  virtual WebExternalTextureLayer* createExternalTextureLayer(
-      cc::TextureLayerClient*) {
-    return nullptr;
-  }
+  virtual std::unique_ptr<WebExternalTextureLayer> createExternalTextureLayer(
+      cc::TextureLayerClient*) = 0;
 
-  virtual WebImageLayer* createImageLayer() { return nullptr; }
+  virtual std::unique_ptr<WebImageLayer> createImageLayer() = 0;
 
-  // The ownership of the WebScrollbarThemeGeometry pointer is passed to
-  // Chromium.
-  virtual WebScrollbarLayer* createScrollbarLayer(WebScrollbar*,
-                                                  WebScrollbarThemePainter,
-                                                  WebScrollbarThemeGeometry*) {
-    return nullptr;
-  }
+  virtual std::unique_ptr<WebScrollbarLayer> createScrollbarLayer(
+      std::unique_ptr<WebScrollbar>,
+      WebScrollbarThemePainter,
+      std::unique_ptr<WebScrollbarThemeGeometry>) = 0;
 
-  virtual WebScrollbarLayer* createSolidColorScrollbarLayer(
+  virtual std::unique_ptr<WebScrollbarLayer> createSolidColorScrollbarLayer(
       WebScrollbar::Orientation,
       int thumbThickness,
       int trackStart,
-      bool isLeftSideVerticalScrollbar) {
-    return nullptr;
-  }
+      bool isLeftSideVerticalScrollbar) = 0;
 
  protected:
   virtual ~WebCompositorSupport() {}
 };
 }
 
 #endif  // WebCompositorSupport_h