Don't require Mac 10.6 SDK for official iOS 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 1575 matching lines @@
         'enable_web_speech%': 0,
         'use_system_libxml%': 1,
         'use_system_sqlite%': 1,
         'locales==': [
           'ar', 'ca', 'cs', 'da', 'de', 'el', 'en-GB', 'en-US', 'es', 'es-MX',
           'fi', 'fr', 'he', 'hi', 'hr', 'hu', 'id', 'it', 'ja', 'ko', 'ms',
           'nb', 'nl', 'pl', 'pt', 'pt-PT', 'ro', 'ru', 'sk', 'sv', 'th', 'tr',
           'uk', 'vi', 'zh-CN', 'zh-TW',
         ],
 
-        # The Mac SDK is set for iOS builds and passed through to Mac
-        # sub-builds. This allows the Mac sub-build SDK in an iOS build to be
-        # overridden from the command line the same way it is for a Mac build.
-        'mac_sdk%': '<!(python <(DEPTH)/build/mac/find_sdk.py 10.6)',
-
         # iOS SDK and deployment target support.  The |ios_sdk| value is left
         # blank so that when it is set in the project files it will be the
         # "current" iOS SDK.  Forcing a specific SDK even if it is "current"
         # causes Xcode to spit out a warning for every single project file for
         # not using the "current" SDK.
         'ios_sdk%': '',
         'ios_sdk_path%': '',
         'ios_deployment_target%': '7.0',
 
         'conditions': [
@@ skipping 220 matching lines @@
           # Chrome normally builds with the Mac OS X 10.6 SDK and sets the
           # deployment target to 10.6.  Other projects, such as O3D, may
           # override these defaults.
 
           # Normally, mac_sdk_min is used to find an SDK that Xcode knows
           # about that is at least the specified version. In official builds,
           # the SDK must match mac_sdk_min exactly. If the SDK is installed
           # someplace that Xcode doesn't know about, set mac_sdk_path to the
           # path to the SDK; when set to a non-empty string, SDK detection
           # based on mac_sdk_min will be bypassed entirely.
-          'mac_sdk_min%': '10.6',
+          'conditions': [
+            ['OS=="ios"', {
+              'mac_sdk_min%': '10.8',
+            }, {  # else OS!="ios"
+              'mac_sdk_min%': '10.6',
+            }],
+          ],
           'mac_sdk_path%': '',
 
           'mac_deployment_target%': '10.6',
         },
 
         'mac_sdk_min': '<(mac_sdk_min)',
         'mac_sdk_path': '<(mac_sdk_path)',
         'mac_deployment_target': '<(mac_deployment_target)',
 
         # Compile in Breakpad support by default so that it can be
         # tested, even if it is not enabled by default at runtime.
         'mac_breakpad_compiled_in%': 1,
         'conditions': [
           # mac_product_name is set to the name of the .app bundle as it should
           # appear on disk.  This duplicates data from
           # chrome/app/theme/chromium/BRANDING and
           # chrome/app/theme/google_chrome/BRANDING, but is necessary to get
           # these names into the build system.
           ['branding=="Chrome"', {
             'mac_product_name%': 'Google Chrome',
           }, { # else: branding!="Chrome"
             'mac_product_name%': 'Chromium',
           }],
-
+          # Official mac builds require a specific OS X SDK, but iOS and
+          # non-official mac builds do not.
+          ['branding=="Chrome" and buildtype=="Official" and OS==mac', {

[xhwang, 2014/10/16 16:55:24]

This should be OS=="mac".

It's causing failures, e.g: 
http://build.chromium.org/p/chromium.chrome/builders/Google%20Chrome%20Mac/bu...

+            'mac_sdk%': '<!(python <(DEPTH)/build/mac/find_sdk.py --verify <(mac_sdk_min) --sdk_path=<(mac_sdk_path))',
+          }, {
+            'mac_sdk%': '<!(python <(DEPTH)/build/mac/find_sdk.py <(mac_sdk_min))',
+          }],
           ['branding=="Chrome" and buildtype=="Official"', {
-            'mac_sdk%': '<!(python <(DEPTH)/build/mac/find_sdk.py --verify <(mac_sdk_min) --sdk_path=<(mac_sdk_path))',
             # Enable uploading crash dumps.
             'mac_breakpad_uploads%': 1,
             # Enable dumping symbols at build time for use by Mac Breakpad.
             'mac_breakpad%': 1,
             # Enable Keystone auto-update support.
             'mac_keystone%': 1,
           }, { # else: branding!="Chrome" or buildtype!="Official"
-            'mac_sdk%': '<!(python <(DEPTH)/build/mac/find_sdk.py <(mac_sdk_min))',
             'mac_breakpad_uploads%': 0,
             'mac_breakpad%': 0,
             'mac_keystone%': 0,
           }],
         ],
       }],  # OS=="mac" or OS=="ios"
       ['OS=="win"', {
         'conditions': [
           # This is the architecture convention used in WinSDK paths.
           ['target_arch=="ia32"', {
@@ skipping 3849 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',
   },
 }