Add way to override optimization level for release build.  
Will be used with valgrind to speed up the bots more.

This was suggested during http://codereview.chromium.org/67199, finally need it.

Review URL: http://codereview.chromium.org/155817

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@21169 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/build/common.gypi b/build/common.gypi
index 2d0cf19..edcd4e4 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -326,8 +326,11 @@
             ],
           },
           'Release': {
+            'variables': {
+              'release_optimize%': '2',
+            },
             'cflags': [
-              '-O2',
+              '-O<(release_optimize)',
               # Don't emit the GCC version ident directives, they just end up
               # in the .comment section taking up binary size.
               '-fno-ident',