Gcc: Suppress warnings in third_party

There's a bit of warning spam when building chrome using gcc.  This CL
suppresses the warnings like we do when using clang.

BUG=697528
R=dominicc@chromium.org,dalecurtis@chromium.org

Review-Url: https://codereview.chromium.org/2783763002
Cr-Original-Commit-Position: refs/heads/master@{#460361}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: aaadc0e2555e316a95b0aaa3fcacb8dcdc2d8044
1 file changed