device/bluetooth: Add BluetoothAdapter::DiscoverySession.

Added the new BluetoothAdapter::DiscoverySession class and
BluetoothAdapter::StartDiscoverySession. This CL implements this
API in a platform independent fashion and marks
BluetoothAdapter::StartDiscovering and BluetoothAdapter::StopDiscovering
as deprecated.

BUG=345008,344995
TEST=device_unittests

Review URL: https://codereview.chromium.org/180783004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254206 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254206
Switch to using the new Link Doctor API.

The new API allows Link Doctor results to be integrated into Chrome's
own error pages.

BUG=64832
R=pkasting@chromium.org, thakis@chromium.org, tsepez@chromium.org, ttuttle@chromium.org

Review URL: https://codereview.chromium.org/137623011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254207 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254207
Make CreateVideoEncodeAccelerator async and create VEA on media thread.

BUG=325984
TEST=trybot

Review URL: https://codereview.chromium.org/144063009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254208 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254208