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

gpu/command_buffer/client/client_context_state.cc

Index: gpu/command_buffer/client/client_context_state.cc
diff --git a/gpu/command_buffer/client/client_context_state.cc b/gpu/command_buffer/client/client_context_state.cc
index df81f30a264b483518de80cf9c4b33131a3e1e89..132142383bddbc1ee31a5f59c0213c7feace7caf 100644
--- a/gpu/command_buffer/client/client_context_state.cc
+++ b/gpu/command_buffer/client/client_context_state.cc
@@ -4,6 +4,8 @@
 
 #include "gpu/command_buffer/client/client_context_state.h"
 
+#include "base/logging.h"
+
 namespace gpu {
 namespace gles2 {
 
@@ -13,6 +15,17 @@ ClientContextState::ClientContextState() {
 ClientContextState::~ClientContextState() {
 }
 
+void ClientContextState::SetViewport(
+    GLint x, GLint y, GLsizei width, GLsizei height) {
+  DCHECK_LE(0, width);
+  DCHECK_LE(0, height);
+
+  viewport_x = x;
+  viewport_y = y;
+  viewport_width = width;
+  viewport_height = height;
+}
+
 // Include the auto-generated part of this file. We split this because it means
 // we can easily edit the non-auto generated parts right here in this file
 // instead of having to edit some template or the code generator.