[v8] Add LTO support for Android Chromium.

build/toolchain.gypi

Index: build/toolchain.gypi
diff --git a/build/toolchain.gypi b/build/toolchain.gypi
index 45c1f9dac8e5658a205c1a977fff318363062ae5..eddc32979fb4524ac6810afa04d071c6813d90ed 100644
--- a/build/toolchain.gypi
+++ b/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"
         ],