(Re-landing http://codereview.chromium.org/5991003)

(Re-landing http://codereview.chromium.org/5991003 after Chromium OS
build fix to browser_render_process_host.cc)

Added group policy for disabling all client-side 3D APIs in Chromium
(in particular, WebGL and Pepper 3D). This has been hooked up through
a new command-line argument (--disable-3d-apis) orthogonal to the
existing ones, so that further changes to those command line arguments
will not accidentally regress the group policy support.

Tested in the following ways:
- Verified that --disable-3d-apis disables WebGL and Pepper 3D
  support on Mac OS X.
- Verified that specifying the Disable3DAPIs policy via a JSON file
  disables WebGL on Linux.
- Ran unit_tests and verified that there were no failures introduced.

BUG=64806
TEST=ConfigurationPolicyPrefStoreBooleanTest


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=69791