Enable libc++ on Android

Switch Chrome on Android to use libc++ instead of stlport. WebView AOSP
builds will continue to use stlport for the time being.

Note that this change is exploratory, and likely to be reverted before
branch point (ensuring WebView and Chrome remain in lockstep with
respect to standard library dependencies).

BUG=427718
TBR=cpu@chromium.org

Review URL: https://codereview.chromium.org/835633003

Cr-Commit-Position: refs/heads/master@{#315085}
14 files changed