Cache GL's viewport on the GPU command buffer client side.

gpu/command_buffer/client/client_context_state.h

 // Copyright (c) 2012 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.
 
 // This file contains the ContextState class.
 
 #ifndef GPU_COMMAND_BUFFER_CLIENT_CLIENT_CONTEXT_STATE_H_
 #define GPU_COMMAND_BUFFER_CLIENT_CLIENT_CONTEXT_STATE_H_
 
 #include <GLES3/gl3.h>
 #include "gles2_impl_export.h"
 
 namespace gpu {
 namespace gles2 {
 
 struct GLES2_IMPL_EXPORT ClientContextState {
   ClientContextState();
   ~ClientContextState();
 
   // Returns true if state was cached in which case 'enabled' will be set to the
   // current state.
   bool GetEnabled(GLenum cap, bool* enabled) const;
 
   // Sets the state of a capability.
   // Returns true if the capability is one that is cached.
   // 'changed' will be true if the state was different from 'enabled.
   bool SetCapabilityState(GLenum cap, bool enabled, bool* changed);
 
+  // Cache the user's valid viewport.
+  void SetViewport(GLint x, GLint y, GLsizei width, GLsizei height);
+
   #include "gpu/command_buffer/client/client_context_state_autogen.h"
 
   EnableFlags enable_flags;
+
+  GLint viewport_x = 0;
+  GLint viewport_y = 0;
+  GLsizei viewport_width = 0;
+  GLsizei viewport_height = 0;
 };
 
 }  // namespace gles2
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_CLIENT_CLIENT_CONTEXT_STATE_H_