Increase minimum iOS version requirements to iOS 9.0.

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 1672 matching lines @@
           'uk', 'vi', 'zh-CN', 'zh-TW',
         ],
 
         # 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',
+        'ios_deployment_target%': '9.0',
 
         'conditions': [
           # ios_product_name is set to the name of the .app bundle as it should
           # appear on disk.
           ['branding=="Chrome"', {
             'ios_product_name%': 'Chrome',
           }, { # else: branding!="Chrome"
             'ios_product_name%': 'Chromium',
           }],
           ['branding=="Chrome" and buildtype=="Official"', {
@@ skipping 4696 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',
   },
 }