mac: Turn on partial availability warning.

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 2560 matching lines @@
     },
     'includes': [ 'set_clang_warning_flags.gypi', ],
     'defines': [
       # Don't use deprecated V8 APIs anywhere.
       'V8_DEPRECATION_WARNINGS',
     ],
     'include_dirs': [
       '<(SHARED_INTERMEDIATE_DIR)',
     ],
     'conditions': [
+      ['OS=="mac"', {
+        # When compiling Objective C, warns if a method is used whose
+        # availability is newer than the deployment target.
+        'xcode_settings': { 'WARNING_CFLAGS': ['-Wpartial-availability']},
+      }],
       ['(OS=="mac" or OS=="ios") and asan==1', {
         'dependencies': [
           '<(DEPTH)/build/mac/asan.gyp:asan_dynamic_runtime',
         ],
       }],
       ['OS=="win" and asan==1 and component=="shared_library"', {
         'dependencies': [
           '<(DEPTH)/build/win/asan.gyp:asan_dynamic_runtime',
         ],
       }],
@@ skipping 3595 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',
   },
 }