Add reference-counting for mailbox textures.

gpu/command_buffer/service/texture_definition.h

Index: gpu/command_buffer/service/texture_definition.h
diff --git a/gpu/command_buffer/service/texture_definition.h b/gpu/command_buffer/service/texture_definition.h
index 9bf0509a825ca7d4d00d558cabd29921137aec53..fec40a7d483a28860416c6d4b0a5d876b3489a24 100644
--- a/gpu/command_buffer/service/texture_definition.h
+++ b/gpu/command_buffer/service/texture_definition.h
@@ -5,9 +5,12 @@
 #ifndef GPU_COMMAND_BUFFER_SERVICE_TEXTURE_DEFINITION_H_
 #define GPU_COMMAND_BUFFER_SERVICE_TEXTURE_DEFINITION_H_
 
+#include <set>
 #include <vector>
 
 #include "base/callback.h"
+#include "base/memory/ref_counted.h"
+#include "base/observer_list.h"
 #include "gpu/command_buffer/service/gl_utils.h"
 #include "gpu/gpu_export.h"
 
@@ -44,7 +47,24 @@ class GPU_EXPORT TextureDefinition {
 
   typedef std::vector<std::vector<LevelInfo> > LevelInfos;
 
-  typedef base::Callback<void(TextureDefinition*)> DestroyCallback;
+  class Client {
+   protected:
+    virtual void StartUsingSharedTexture(TextureDefinition* definition) const;
+    virtual bool StopUsingSharedTexture(TextureDefinition* definition,
+                                        bool delete_texture) const;
+    void StartSharedTextureTransfer(TextureDefinition* definition) const;
+    size_t GetSharedTextureRefCount(TextureDefinition* definition) const {
+      return definition->active_clients_.size();
+    }
+  };
+
+  class Observer {
+   public:
+    virtual void OnDestroySharedTexture(const TextureDefinition* definition) {}
+
+   protected:
+    ~Observer() {}
+  };
 
   TextureDefinition(GLenum target,
                     GLuint service_id,
@@ -55,13 +75,14 @@ class GPU_EXPORT TextureDefinition {
                     GLenum usage,
                     bool immutable,
                     const LevelInfos& level_infos);
-  ~TextureDefinition();
+
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
 
   GLenum target() const {
     return target_;
   }
 
-  GLuint ReleaseServiceId();
   GLuint service_id() const { return service_id_; }
   GLenum min_filter() const { return min_filter_; }
   GLenum mag_filter() const { return mag_filter_; }
@@ -71,11 +92,17 @@ class GPU_EXPORT TextureDefinition {
 
   bool immutable() const { return immutable_; }
 
-  const LevelInfos& level_infos() const {
+  LevelInfos& level_infos() {
     return level_infos_;
   }
 
+  // A static definition for a 2D texture of size 0x0.
+  static TextureDefinition kEmptyTexture2D;
+
  private:
+  ~TextureDefinition();
+  GLuint ReleaseServiceId(bool delete_texture);
+
   GLenum target_;
   GLuint service_id_;
   GLenum min_filter_;
@@ -85,6 +112,13 @@ class GPU_EXPORT TextureDefinition {
   GLenum usage_;
   bool immutable_;
   std::vector<std::vector<LevelInfo> > level_infos_;
+  ObserverList<Observer> observers_;
+
+  typedef std::set<const Client*> ClientList;
+  mutable ClientList active_clients_;
+  const Client* client_transferred_from_;
+
+  static std::set<GLuint> shared_texture_ids_;
 
   DISALLOW_COPY_AND_ASSIGN(TextureDefinition);
 };