Add LTO support for Android Chromium.

This is to add support for a Link-Time Optimizations experiment in Android Chromium. As it is disabled by default, it won't change anything for most configurations.

R=ulan@chromium.org

Review URL: https://codereview.chromium.org/497713002

Patch from Fabrice de Gans <fdegans@chromium.org>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23336 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

build/toolchain.gypi

@@ -91,6 +91,9 @@
     # Allow to suppress the array bounds warning (default is no suppression).
     'wno_array_bounds%': '',
 
+    # Link-Time Optimizations
+    'use_lto%': 0,
+
     'variables': {
       # This is set when building the Android WebView inside the Android build
       # system, using the 'android' gyp backend.
@@ -241,6 +244,15 @@
                   }],
                 ],
               }],
+              # Disable LTO for v8
+              # v8 is optimized for speed, which takes precedence over
+              # size optimization in LTO.
+              ['use_lto==1', {
+                'cflags!': [
+                  '-flto',
+                  '-ffat-lto-objects',
+                ],
+              }],
             ],
           }],  # _toolset=="target"
         ],