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 134 matching lines @@
                 '../chrome/chrome.gyp:linux_packages_<(channel)',
               ],
             }],
             ['enable_ipc_fuzzer==1', {
               'dependencies': [
                 '../tools/ipc_fuzzer/ipc_fuzzer.gyp:*',
               ],
             }],
           ],
         }],
+        ['chromecast==1', {
+          'dependencies': [
+            '../chromecast/chromecast.gyp:*',
+          ],
+        }],
         ['use_x11==1', {
           'dependencies': [
             '../tools/xdisplaycheck/xdisplaycheck.gyp:*',
           ],
         }],
         ['OS=="win"', {
           'conditions': [
             ['win_use_allocator_shim==1', {
               'dependencies': [
                 '../base/allocator/allocator.gyp:*',
@@ skipping 1068 matching lines @@
           'dependencies': [
             '../ui/views/examples/examples.gyp:views_examples_with_content_exe',
             '../ui/views/views.gyp:views',
             '../ui/views/views.gyp:views_unittests',
           ],
         },  # target_name: macviews_builder
       ],  # targets
     }],  # os=='mac' and toolkit_views==1
   ],  # conditions
 }