Add Link-Time Optimizations support for Android.

build/android/increase_size_for_speed.gypi

 # Copyright (c) 2014 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.
 
 # This file is meant to be included to optimize a target for speed
 # rather than for size on Android.
 # This is used in some carefully tailored targets and is not meant
 # to be included everywhere. Before adding the template to another target,
 # please ask in chromium-dev@. See crbug.com/411909
 
 {
   'configurations': {
     'Release': {
       'target_conditions': [
         ['_toolset=="target"', {
           'conditions': [
             ['OS=="android"', {
               'cflags!': ['-Os'],
               'cflags': ['-O2'],
             }],
+            # Do not merge -Os and -O2 in LTO.
+            # LTO merges all optimization options at link-time. -O2 takes
+            # precedence over -Os. Avoid using LTO simultaneously
+            # on -Os and -O2 parts for that reason.

[tomhudson, 2014/10/13 16:41:11]

Seems like this comment applies to the above condition, rather than the below
conditions?

[Fabrice (no longer in Chrome), 2014/10/14 14:58:55]

No, it's to the below conditions. We remove the -flto flags for targets compiled
with -O2 if we're using the use_lto gyp flag.
On the other hand, we add the -flto flags if we're using the use_lto_o2 gyp
flag.

+            ['use_lto==1', {
+              'cflags!': [
+                '-flto',
+                '-ffat-lto-objects',
+              ],
+            }],
+            ['use_lto_o2==1', {
+              'cflags': [
+                '-flto',
+                '-ffat-lto-objects',
+              ],
+            }],
           ],
         }],
       ],
     },
   },
 }