Update Context Client Visibility to use Scoped Pattern

gpu/command_buffer/client/context_support.h

Index: gpu/command_buffer/client/context_support.h
diff --git a/gpu/command_buffer/client/context_support.h b/gpu/command_buffer/client/context_support.h
index 99e94045326adf8b4abcd2acd1570f085789ee9d..543025d81045b94737446e3bd0c8b457a511f2f1 100644
--- a/gpu/command_buffer/client/context_support.h
+++ b/gpu/command_buffer/client/context_support.h
@@ -29,11 +29,8 @@ class ContextSupport {
   // 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;
@@ -56,8 +53,10 @@ class ContextSupport {
   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: