Update Context Client Visibility to use Scoped Pattern

gpu/command_buffer/client/context_support.h

 // 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.
 
 #ifndef GPU_COMMAND_BUFFER_CLIENT_CONTEXT_SUPPORT_H_
 #define GPU_COMMAND_BUFFER_CLIENT_CONTEXT_SUPPORT_H_
 
 #include <stdint.h>
 
 #include "base/callback.h"
@@ skipping 11 matching lines @@
 class ContextSupport {
  public:
   // Runs |callback| when a sync token is signalled.
   virtual void SignalSyncToken(const SyncToken& sync_token,
                                const base::Closure& callback) = 0;
 
   // Runs |callback| when a query created via glCreateQueryEXT() has cleared
   // passed the glEndQueryEXT() point.
   virtual void SignalQuery(uint32_t query, const base::Closure& callback) = 0;
 
-  // Indicates whether the context should aggressively free allocated resources.
-  // If set to true, the context will purge all temporary resources when
-  // flushed.
-  virtual void SetAggressivelyFreeResources(
-      bool aggressively_free_resources) = 0;
+  // Causes ContextSupport to trim allocated resources, reducing memory usage.
+  virtual void TrimResources() = 0;
 
   virtual void Swap() = 0;
   virtual void PartialSwapBuffers(const gfx::Rect& sub_buffer) = 0;
   virtual void CommitOverlayPlanes() = 0;
 
   // Schedule a texture to be presented as an overlay synchronously with the
   // primary surface during the next buffer swap or CommitOverlayPlanes.
   // This method is not stateful and needs to be re-scheduled every frame.
   virtual void ScheduleOverlayPlane(int plane_z_order,
                                     gfx::OverlayTransform plane_transform,
                                     unsigned overlay_texture_id,
                                     const gfx::Rect& display_bounds,
                                     const gfx::RectF& uv_rect) = 0;
 
   // Returns an ID that can be used to globally identify the share group that
   // this context's resources belong to.
   virtual uint64_t ShareGroupTracingGUID() const = 0;
 
   // Sets a callback to be run when an error occurs.
   virtual void SetErrorMessageCallback(
       const base::Callback<void(const char*, int32_t)>& callback) = 0;
 
-  // Called when a client of the context has changed visibility.
-  virtual void SetClientVisible(int client_id, bool is_visible) = 0;
+  class ScopedVisibility {};
+  virtual std::unique_ptr<ScopedVisibility> ClientBecameVisible() = 0;
+  virtual void ClientBecameNotVisible(
+      std::unique_ptr<ScopedVisibility> visibility) = 0;
   virtual bool AnyClientsVisible() const = 0;
 
  protected:
   ContextSupport() {}
   virtual ~ContextSupport() {}
 };
 
 }
 
 #endif  // GPU_COMMAND_BUFFER_CLIENT_CONTEXT_SUPPORT_H_