Move code around to fix build with system mesa.

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index 6f450a21e81cada13f4fc3ac79f8b8a09dc22a52..2c1a46891037e2d500dadfe5b7db5a2a6751034b 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -56,6 +56,7 @@
 #include "gpu/command_buffer/service/texture_manager.h"
 #include "gpu/command_buffer/service/vertex_attrib_manager.h"
 #include "gpu/command_buffer/service/vertex_array_manager.h"
+#include "gpu/GLES2/gl2chromium_constants.h"
 #include "ui/gl/async_pixel_transfer_delegate.h"
 #include "ui/gl/gl_image.h"
 #include "ui/gl/gl_implementation.h"
@@ -64,10 +65,6 @@
 #include "ui/surface/io_surface_support_mac.h"
 #endif
 
-#if !defined(GL_DEPTH24_STENCIL8)
-#define GL_DEPTH24_STENCIL8 0x88F0
-#endif
-
 // TODO(zmo): we can't include "City.h" due to type def conflicts.
 extern uint64 CityHash64(const char*, size_t);