Make target running GLES2 autogen script.

gpu/command_buffer/build_gles2_cmd_buffer.py

Index: gpu/command_buffer/build_gles2_cmd_buffer.py
diff --git a/gpu/command_buffer/build_gles2_cmd_buffer.py b/gpu/command_buffer/build_gles2_cmd_buffer.py
index 522be5e114c64725a9cbf512ba5362ee8f24bf54..93b13ea6f18ccc97beb972f566b7dfc2b688f190 100755
--- a/gpu/command_buffer/build_gles2_cmd_buffer.py
+++ b/gpu/command_buffer/build_gles2_cmd_buffer.py
@@ -5400,28 +5400,41 @@ def main(argv):
   parser.add_option(
       "--alternate-mode", type="choice",
       choices=("ppapi", "chrome_ppapi"),
-      help="generate files for other projects. \"ppapi\" must be run from the "
-      "directory containing the ppapi directory, and will generate ppapi "
-      "bindings. \"chrome_ppapi\" must be run from chrome src directory and "
-      "will generate chrome plumbing for ppapi.")
+      help="generate files for other projects. \"ppapi\" will generate ppapi "
+      "bindings. \"chrome_ppapi\" generate chrome implementation for ppapi.")
+  parser.add_option(
+      "--output-dir",
+      help="base directory for resulting files, under chrome/src. default is "
+      "empty. Use this if you want the result stored under gen.")
   parser.add_option(
       "-v", "--verbose", action="store_true",
       help="prints more output.")
 
   (options, args) = parser.parse_args(args=argv)
 
+  # This script lives under gpu/command_buffer, cd to base directory.
+  os.chdir(os.path.dirname(__file__) + "/../..")
+
   gen = GLGenerator(options.verbose)
   gen.ParseGLH("common/GLES2/gl2.h")
 
+  # Support generating files under gen/
+  if options.output_dir != None:
+    os.chdir(options.output_dir)
+
   if options.alternate_mode == "ppapi":
-    gen.WritePepperGLES2Interface("ppapi/c/dev/ppb_opengles_dev.h")
-    gen.WriteGLES2ToPPAPIBridge("ppapi/lib/gl/gles2/gles2.c")
+    # To trigger this action, do "make ppapi_gles_bindings"
+    os.chdir("ppapi");
+    gen.WritePepperGLES2Interface("c/dev/ppb_opengles_dev.h")
+    gen.WriteGLES2ToPPAPIBridge("lib/gl/gles2/gles2.c")
 
   elif options.alternate_mode == "chrome_ppapi":
+    # To trigger this action, do "make ppapi_gles_implementation"
     gen.WritePepperGLES2Implementation(
         "webkit/plugins/ppapi/ppb_opengles_impl.cc")
 
   else:
+    os.chdir("gpu/command_buffer")
     gen.WriteCommandIds("common/gles2_cmd_ids_autogen.h")
     gen.WriteFormat("common/gles2_cmd_format_autogen.h")
     gen.WriteFormatTest("common/gles2_cmd_format_test_autogen.h")