Removed mtune for Android build.

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 1852 matching lines @@
       # Set default compiler flags depending on ARM version.
       ['arm_version==6 and android_webview_build==0', {
         'arm_arch%': 'armv6',
         'arm_tune%': '',
         'arm_fpu%': 'vfp',
         'arm_float_abi%': 'softfp',
         'arm_thumb%': 0,
       }],
       ['arm_version==7 and android_webview_build==0', {
         'arm_arch%': 'armv7-a',
-        'arm_tune%': 'cortex-a8',
+        'arm_tune%': '',
         'conditions': [
           ['arm_neon==1', {
             'arm_fpu%': 'neon',
           }, {
             'arm_fpu%': 'vfpv3-d16',
           }],
         ],
         # Change the default to hard once the armhf transition is complete.
         'arm_float_abi%': 'softfp',
         'arm_thumb%': 1,
@@ skipping 2947 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',
   },
 }