Refactor client visibility handling

gpu/command_buffer/client/gles2_implementation.h

Index: gpu/command_buffer/client/gles2_implementation.h
diff --git a/gpu/command_buffer/client/gles2_implementation.h b/gpu/command_buffer/client/gles2_implementation.h
index 53a248e12e8fdb28569c28f723bcdff6c2b7850a..c877b0f88262080f4821a9fc063626df12e4e66d 100644
--- a/gpu/command_buffer/client/gles2_implementation.h
+++ b/gpu/command_buffer/client/gles2_implementation.h
@@ -199,8 +199,6 @@ class GLES2_IMPL_EXPORT GLES2Implementation
   uint64_t ShareGroupTracingGUID() const override;
   void SetErrorMessageCallback(
       const base::Callback<void(const char*, int32_t)>& callback) override;
-  void SetClientVisible(int client_id, bool is_visible) override;
-  bool AnyClientsVisible() const override;
 
   // TODO(danakj): Move to ContextSupport once ContextProvider doesn't need to
   // intercept it.
@@ -823,9 +821,6 @@ class GLES2_IMPL_EXPORT GLES2Implementation
   // whether it should aggressively free them.
   bool aggressively_free_resources_;
 
-  // The set of IDs of all visible clients.
-  std::set<int> visible_clients_;
-
   // Result of last GetString(GL_EXTENSIONS), used to keep
   // GetString(GL_EXTENSIONS), GetStringi(GL_EXTENSIONS, index) and
   // GetIntegerv(GL_NUM_EXTENSIONS) in sync. This points to gl_strings, valid