Make it possible to switch between two different versions of ANGLE.

build/all.gyp

 # 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.
 
 {
   'targets': [
     {
       'target_name': 'All',
       'type': 'none',
       'xcode_create_dependents_test_runner': 1,
@@ skipping 128 matching lines @@
                 # TODO(jschuh) Enable Win64 Chrome Frame. crbug.com/176875
                 '../chrome_frame/chrome_frame.gyp:*',
               ],
             }],
           ],
           'dependencies': [
             '../cloud_print/cloud_print.gyp:*',
             '../courgette/courgette.gyp:*',
             '../rlz/rlz.gyp:*',
             '../sandbox/sandbox.gyp:*',
-            '../third_party/angle/src/build_angle.gyp:*',
+            '<(angle_path)/src/build_angle.gyp:*',
             '../third_party/bsdiff/bsdiff.gyp:*',
             '../third_party/bspatch/bspatch.gyp:*',
             '../third_party/gles2_book/gles2_book.gyp:*',
           ],
         }, {
           'dependencies': [
             '../third_party/libevent/libevent.gyp:*',
           ],
         }],
         ['toolkit_views==1', {
@@ skipping 723 matching lines @@
             '../chrome/chrome.gyp:interactive_ui_tests_run',
             '../chrome/chrome.gyp:sync_integration_tests_run',
             '../chrome/chrome.gyp:unit_tests_run',
             '../net/net.gyp:net_unittests_run',
           ],
         }, # target_name: chromium_swarm_tests
       ],
     }],
   ], # conditions
 }