exo: Handle lost context situations properly.

components/exo/buffer.h

Index: components/exo/buffer.h
diff --git a/components/exo/buffer.h b/components/exo/buffer.h
index 192513b63bc3144d3a0349bd03ec62bfb441724c..2f60f5b9f7fa3c7b0ed21e43858ca4b7cf06d0df 100644
--- a/components/exo/buffer.h
+++ b/components/exo/buffer.h
@@ -9,9 +9,6 @@
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
-#include "gpu/command_buffer/common/mailbox.h"
-#include "gpu/command_buffer/common/sync_token.h"
-#include "ui/gfx/buffer_types.h"
 #include "ui/gfx/geometry/size.h"
 
 namespace base {
@@ -29,6 +26,10 @@ namespace gfx {
 class GpuMemoryBuffer;
 }
 
+namespace gpu {
+struct SyncToken;
+}
+
 namespace exo {
 
 // This class provides the content for a Surface. The mechanism by which a
@@ -50,7 +51,7 @@ class Buffer : public base::SupportsWeakPtr<Buffer> {
   // This function can be used to acquire a texture mailbox that is bound to
   // the buffer. Returns a release callback on success. The release callback
   // must be called before a new texture mailbox can be acquired.
-  scoped_ptr<cc::SingleReleaseCallback> AcquireTextureMailbox(
+  scoped_ptr<cc::SingleReleaseCallback> ProduceTextureMailbox(
       cc::TextureMailbox* mailbox);
 
   // Returns the size of the buffer.
@@ -60,18 +61,38 @@ class Buffer : public base::SupportsWeakPtr<Buffer> {
   scoped_refptr<base::trace_event::TracedValue> AsTracedValue() const;
 
  private:
-  static void Release(base::WeakPtr<Buffer> buffer,
-                      unsigned texture_target,
-                      unsigned texture_id,
-                      unsigned image_id,
-                      const gpu::SyncToken& sync_token,
-                      bool is_lost);
-
+  class Texture;
+
+  // Decrements the use count of buffer and notifies the client that buffer
+  // as been released if it reached 0.
+  void Release();
+
+  // This is used by ProduceTextureMailbox() to produce a release callback
+  // that releases the buffer contents referenced by a texture before the
+  // texture is destroyed or reused.
+  // Note: This is a static function as it needs to run even if the buffer
+  // has been destroyed.
+  static void ReleaseTexture(base::WeakPtr<Buffer> buffer,
+                             scoped_ptr<Texture> texture,
+                             const gpu::SyncToken& sync_token,
+                             bool is_lost);
+
+  // The GPU memory buffer that contains the contents of this buffer.
   scoped_ptr<gfx::GpuMemoryBuffer> gpu_memory_buffer_;
+
+  // Texture target that must be used when creating a texture for buffer.
   const unsigned texture_target_;
-  unsigned texture_id_;
-  unsigned image_id_;
-  gpu::Mailbox mailbox_;
+
+  // This is incremented when a texture mailbox is produced and decremented
+  // when a texture mailbox is released. It is used to determine when we should
+  // notify the client that buffer has been released.
+  unsigned use_count_;
+
+  // The last released texture instance. ProduceTextureMailbox() will use this
+  // instead of creating a new texture when possible.
+  scoped_ptr<Texture> last_texture_;
+
+  // The client release callback.
   base::Closure release_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(Buffer);