ios: Switch from -std=gnu++0x to -std=c++11.

BUG=427584

Review URL: https://codereview.chromium.org/693893004

Cr-Commit-Position: refs/heads/master@{#302644}

build/common.gypi

@@ -5151,9 +5151,7 @@
     ['OS=="ios"', {
       'target_defaults': {
         'xcode_settings' : {
-          # TODO(stuartmorgan): switch to c++0x (see TODOs in the clang
-          # section above).
-          'CLANG_CXX_LANGUAGE_STANDARD': 'gnu++0x',
+          'CLANG_CXX_LANGUAGE_STANDARD': 'c++11',
 
           'conditions': [
             # Older Xcodes do not support -Wno-deprecated-register, so pass an