Fix ENABLE_SWIFTSHADER flag.

ui/gl/BUILD.gn

 # Copyright 2014 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.
 
+import("//build/buildflag_header.gni")
+import("//build/config/chrome_build.gni")
 import("//build/config/linux/pkg_config.gni")
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 
+declare_args() {
+  enable_swiftshader = is_chrome_branded && is_win

[Nico, 2016/09/15 15:47:33]

could we start with this set to false, and then flip this in a separate cl?
as-is, the cl description sounds like this just adds a flag, not that it
actually changes behavior on windows

also, why do we enable this only in branded builds? we try to keep chromium and
chrome as similar as possible (but i suppose that's a question for the follow-up
with the actual switch)

+}
+
 use_egl = is_win || is_android || is_linux
 use_glx = use_x11
 
 if (is_android) {
   import("//build/config/android/config.gni")
   import("//build/config/android/rules.gni")
 }
 
+buildflag_header("gl_features") {
+  header = "gl_features.h"
+  flags = [ "ENABLE_SWIFTSHADER=$enable_swiftshader" ]
+}
+
 config("gl_config") {
   defines = []
   if (use_glx) {
     defines += [
       "GL_GLEXT_PROTOTYPES",
       "USE_GLX",
     ]
   }
   if (use_egl) {
     defines += [ "USE_EGL" ]
@@ skipping 369 matching lines @@
     sources = [
       "../android/java/src/org/chromium/ui/gl/SurfaceTextureListener.java",
       "../android/java/src/org/chromium/ui/gl/SurfaceTexturePlatformWrapper.java",
     ]
     public_deps = [
       ":surface_jni_headers",
     ]
     jni_package = "ui/gl"
   }
 }