Implement EXT_draw_buffers WebGL extention support in command buffer.

gpu/command_buffer/client/gles2_implementation_unittest_autogen.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 is auto-generated from
 // gpu/command_buffer/build_gles2_cmd_buffer.py
 // DO NOT EDIT!
 
 // This file is included by gles2_implementation.h to declare the
 // GL api functions.
@@ skipping 1780 matching lines @@
 TEST_F(GLES2ImplementationTest, WaitSyncPointCHROMIUM) {
   struct Cmds {
     cmds::WaitSyncPointCHROMIUM cmd;
   };
   Cmds expected;
   expected.cmd.Init(1);
 
   gl_->WaitSyncPointCHROMIUM(1);
   EXPECT_EQ(0, memcmp(&expected, commands_, sizeof(expected)));
 }
+
+TEST_F(GLES2ImplementationTest, DrawBuffersEXT) {
+  struct Cmds {
+    cmds::DrawBuffersEXTImmediate cmd;
+    GLenum data[1][1];
+  };
+
+  Cmds expected;
+  for (int ii = 0; ii < 1; ++ii) {
+    for (int jj = 0; jj < 1; ++jj) {
+      expected.data[ii][jj] = static_cast<GLenum>(ii * 1 + jj);
+    }
+  }
+  expected.cmd.Init(1, &expected.data[0][0]);
+  gl_->DrawBuffersEXT(1, &expected.data[0][0]);
+  EXPECT_EQ(0, memcmp(&expected, commands_, sizeof(expected)));
+}
 #endif  // GPU_COMMAND_BUFFER_CLIENT_GLES2_IMPLEMENTATION_UNITTEST_AUTOGEN_H_