GitLab

Tune global Android ARM cflags for performance.
Update cflags in gn to keep up with gyp.

BUG=407545
CQ_TRYBOTS=tryserver.chromium.linux:android_aosp,android_clang_dbg,android_dbg

Review URL: https://codereview.chromium.org/375483003

Cr-Commit-Position: refs/heads/master@{#293913}