Enable gbm platform by default in ozone builds

build/common.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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 2367 matching lines @@
       ['chromeos==1', {
         'use_brlapi%': 1,
       }],
 
       ['use_ozone==1 and ozone_auto_platforms==1', {
         # Use test as the default platform.
         'ozone_platform%': 'test',
 
         # Build all platforms whose deps are in install-build-deps.sh.
         # Only these platforms will be compile tested by buildbots.
+        'ozone_platform_gbm%': 1,
         'ozone_platform_drm%': 1,
         'ozone_platform_test%': 1,
         'ozone_platform_egltest%': 1,
       }],
 
       ['desktop_linux==1 and use_aura==1 and use_x11==1', {
         'use_clipboard_aurax11%': 1,
       }],
 
       ['OS=="win" and use_goma==1', {
@@ skipping 3902 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }