Replace WTF::Optional the base::Optional implementation.

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 3900 matching lines @@
                   '-m64',
                 ],
               }],
             ],
           }],
           ['target_arch=="arm"', {
             'target_conditions': [
               ['_toolset=="target"', {
                 'conditions': [
                   ['clang==0', {
+                    'cflags': [
+                      # Don't warn about "maybe" uninitialized. Clang doesn't
+                      # include this in -Wall but gcc does, and it gives false
+                      # positives.
+                      '-Wno-maybe-uninitialized',
+                    ],
                     'cflags_cc': [
                       # The codesourcery arm-2009q3 toolchain warns at that the ABI
                       # has changed whenever it encounters a varargs function. This
                       # silences those warnings, as they are not helpful and
                       # clutter legitimate warnings.
                       '-Wno-abi',
                     ],
                   }],
                   ['clang==1 and arm_arch!="" and OS!="android"', {
                     'cflags': [
@@ skipping 2386 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',
   },
 }