Remove outdated comment from common.gypi.

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 1513 matching lines @@
       ['OS=="mac"', {
         'conditions': [
           # All Chrome builds have breakpad symbols, but only process the
           # symbols from official builds.
           ['(branding=="Chrome" and buildtype=="Official")', {
             'mac_strip_release%': 1,
           }],
         ],
       }],  # OS=="mac"
       ['OS=="mac" or OS=="ios"', {
-        # Enable clang on mac by default!  All iOS builds already use clang.
         'clang%': 1,
 
         'variables': {
           # Mac OS X SDK and deployment target support.  The SDK identifies
           # the version of the system headers that will be used, and
           # corresponds to the MAC_OS_X_VERSION_MAX_ALLOWED compile-time
           # macro.  "Maximum allowed" refers to the operating system version
           # whose APIs are available in the headers.  The deployment target
           # identifies the minimum system version that the built products are
           # expected to function on.  It corresponds to the
@@ skipping 3478 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',
   },
 }