[Mac] GTM role to pick up a newer GTM that include a workaround for when Coco...

DEPS

 vars = {
   "webkit_trunk":
     "http://svn.webkit.org/repository/webkit/trunk",
   "webkit_revision": "56239",
   "ffmpeg_revision": "42082",
   "skia_revision": "504",
   "chromium_git": "http://src.chromium.org/git",
   "swig_revision": "40423",
   "nacl_revision": "1742",
 }
@@ skipping 133 matching lines @@
     "src/third_party/mingw-w64/mingw/bin":
       ("http://nativeclient.googlecode.com/svn/trunk/src/third_party/mingw-w64/mingw/bin@" +
        Var("nacl_revision")),
 
   },
   "mac": {
     "src/chrome/tools/test/reference_build/chrome_mac":
       "/trunk/deps/reference_builds/chrome_mac@41963",
 
     "src/third_party/GTM":
-      "http://google-toolbox-for-mac.googlecode.com/svn/trunk@310",
+      "http://google-toolbox-for-mac.googlecode.com/svn/trunk@312",
     "src/third_party/pdfsqueeze":
       "http://pdfsqueeze.googlecode.com/svn/trunk@2",
     "src/third_party/lighttpd":
       "/trunk/deps/third_party/lighttpd@33737",
 
     "src/third_party/WebKit/WebKit/mac":
       Var("webkit_trunk") + "/WebKit/mac@" + Var("webkit_revision"),
     "src/third_party/WebKit/WebKitLibraries":
       Var("webkit_trunk") + "/WebKitLibraries@" + Var("webkit_revision"),
 
@@ skipping 67 matching lines @@
     "action": ["python", "src/build/gyp_chromium"],
   },
   {
     # Workaround XCode dependecies problem.
     # TODO(bradnelson): remove this when fixed.
     "pattern": ".",
     "action": ["python",
                "src/build/mac/clobber_generated_headers.py"],
   },
 ]