Add chromecast_build gyp variable and add rules when the variable is set to 1.

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.
 
 {
   'variables': {
     # A hook that can be overridden in other repositories to add additional
     # compilation targets to 'All'. Only used on Android.
     'android_app_targets%': [],
   },
@@ skipping 136 matching lines @@
                 '../third_party/mtpd/mtpd.gyp:*',
               ],
             }],
             ['enable_ipc_fuzzer==1', {
               'dependencies': [
                 '../tools/ipc_fuzzer/ipc_fuzzer.gyp:*',
               ],
             }],
           ],
         }],
+        ['chromecast_build==1', {
+          'dependencies': [
+            '../chromecast/chromecast.gyp:*',
+          ],
+        }],
         ['use_x11==1', {
           'dependencies': [
             '../tools/xdisplaycheck/xdisplaycheck.gyp:*',
           ],
         }],
         ['toolkit_uses_gtk==1', {
           'dependencies': [
             '../tools/gtk_clipboard_dump/gtk_clipboard_dump.gyp:*',
           ],
         }],
@@ skipping 1068 matching lines @@
             # http://crbug.com/157234
             #'../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
 }