base: Refactor DiscardableMemoryProvider to build and be tested on all platforms.

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 620 matching lines @@
 
         # Android OS includes support for proprietary codecs regardless of
         # building Chromium or Google Chrome. We also ship Google Chrome with
         # proprietary codecs.
         ['OS=="android" or branding=="Chrome"', {
           'proprietary_codecs%': 1,
         }, {
           'proprietary_codecs%': 0,
         }],
 
-        ['OS=="mac"', {
+        ['OS=="mac" or OS=="ios"', {

[reveman, 2013/12/14 05:32:59]

How this worked before is a mystery to me.

[reveman, 2013/12/14 07:42:01]

Ok, looks like we built both discardable_memory_mac.cc and
discardable_memory_emulated.cc on ios before this change and
DiscardableMemory::SupportedNatively symbol was defined twice withiout the
linker complaining!

           'native_discardable_memory%': 1,
           'native_memory_pressure_signals%': 1,
         }],
 
         # Enable autofill dialog for Android, Mac and Views-enabled platforms.
         ['toolkit_views==1 or (OS=="android" and android_webview_build==0) or OS=="mac"', {
           'enable_autofill_dialog%': 1
         }],
 
         ['OS=="android" and android_webview_build==0', {
@@ skipping 4137 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',
   },
 }