Fix ninja build for android.

content/content_shell.gypi

 # 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.
 
 {
   'variables': {
     'content_shell_product_name': 'Content Shell',
   },
   'targets': [
     {
@@ skipping 561 matching lines @@
               ],
               'outputs': [
                 # Awkwardly, we build a Debug APK even when gyp is in
                 # Release mode.  I don't think it matters (e.g. we're
                 # probably happy to not codesign) but naming should be
                 # fixed.
                 '<(PRODUCT_DIR)/ContentShell-debug.apk',
               ],
               'action': [
                 'ant',
-                '-DPRODUCT_DIR=<(PRODUCT_DIR)',
+                '-DPRODUCT_DIR=<(absolute_product_dir)',
                 '-DAPP_ABI=<(android_app_abi)',
                 '-buildfile',
                 '<(DEPTH)/content/shell/android/content_shell_apk.xml',
               ]
             }
           ],
         },
       ],
     }],  # OS=="android"
   ]
 }