ios: Enable -Wunused-functions.

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 4213 matching lines @@
           # section above).
           'CLANG_CXX_LANGUAGE_STANDARD': 'gnu++0x',
           # Warn if automatic synthesis is triggered with
           # the -Wobjc-missing-property-synthesis flag.
           'CLANG_WARN_OBJC_MISSING_PROPERTY_SYNTHESIS': 'YES',
           'WARNING_CFLAGS': [
             '-Wheader-hygiene',
             # Don't die on dtoa code that uses a char as an array index.
             # This is required solely for base/third_party/dmg_fp/dtoa.cc.
             '-Wno-char-subscripts',
-            # Clang spots more unused functions. TODO: remove, crbug.com/315884
-            '-Wno-unused-function',
+            # See comment in the mac clang section above for this flag.
+            '-Wno-unneeded-internal-declaration',
             # Match OS X clang C++11 warning settings.
             '-Wno-c++11-narrowing',
           ],
         },
         'target_conditions': [
           ['_toolset=="host"', {
             'xcode_settings': {
               'SDKROOT': 'macosx<(mac_sdk)',  # -isysroot
               'MACOSX_DEPLOYMENT_TARGET': '<(mac_deployment_target)',
               'ARCHS': [
@@ skipping 456 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',
   },
 }