Linux/CrOS/Cast/Android (and Mac with gn): Build chromium_code with -Wextra.

Source: codereview.chromium.org --- Thursday, December 31, 2015
Linux/CrOS/Cast/Android (and Mac with gn): Build chromium_code with -Wextra. Lands the -Wextra bits of http://ift.tt/1mTSQx5 (reviewed there). Windows, Mac, and iOS already build chromium_code with -Wextra. (Mac and iOS only in the gyp build, not in gn yet.) This makes the other platforms match and also adds -Wextra to chromium_code in gn builds. BUG=573250,572776 TBR=thestig@chromium.org ...

from Windows http://ift.tt/1YUOiSP