Change PluginWindowHandle type to be bool on Mac.

The change this was waiting on (removing windowed plugins) has
been in effect for a long time. Also delete unused IPC messages.

BUG=314190
R=ben@chromium.org

Review URL: https://codereview.chromium.org/138423003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244967 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 244967
Don't pass thumb-interwork to clang in the GN build.

This duplicates logic in common.gypi.

R=scottmg@chromium.org
TBR=scottmg

Review URL: https://codereview.chromium.org/139883002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244968 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 244968