Update from https://crrev.com/306655

ui/gl/gl_bindings.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.
 
 #ifndef UI_GL_GL_BINDINGS_H_
 #define UI_GL_GL_BINDINGS_H_
 
 // Includes the platform independent and platform dependent GL headers.
 // Only include this in cc files. It pulls in system headers, including
 // the X11 headers on linux, which define all kinds of macros that are
@@ skipping 254 matching lines @@
 #define GL_CONTEXT_ROBUST_ACCESS_KHR      0x90F3
 #define GL_LOSE_CONTEXT_ON_RESET_KHR      0x8252
 #define GL_GUILTY_CONTEXT_RESET_KHR       0x8253
 #define GL_INNOCENT_CONTEXT_RESET_KHR     0x8254
 #define GL_UNKNOWN_CONTEXT_RESET_KHR      0x8255
 #define GL_RESET_NOTIFICATION_STRATEGY_KHR 0x8256
 #define GL_NO_RESET_NOTIFICATION_KHR      0x8261
 #define GL_CONTEXT_LOST_KHR               0x0507
 #endif /* GL_KHR_robustness */
 
+#ifndef GL_EXT_texture_rg
+#define GL_EXT_texture_rg 1
+#define GL_RED_EXT 0x1903
+#define GL_RG_EXT 0x8227
+#define GL_R8_EXT 0x8229
+#define GL_RG8_EXT 0x822B
+#endif /* GL_EXT_texture_rg */
+
 #define GL_GLEXT_PROTOTYPES 1
 
 #if defined(OS_WIN)
 #define GL_BINDING_CALL WINAPI
 #else
 #define GL_BINDING_CALL
 #endif
 
 #define GL_SERVICE_LOG(args) DLOG(INFO) << args;
 #if defined(NDEBUG)
@@ skipping 126 matching lines @@
 #elif defined(OS_ANDROID)
 
 GL_EXPORT extern EGLApi* g_current_egl_context;
 GL_EXPORT extern DriverEGL g_driver_egl;
 
 #endif
 
 }  // namespace gfx
 
 #endif  // UI_GL_GL_BINDINGS_H_