Enable virtual context on IMG devices only.

Enable virtual context on IMG devices only.

This adds booleans to feature_info for all the common Android vendors
and turns on virtual contexts for IMG only, as there are remaining bugs
with the other architectures (and IMG is the main reason we are working
on virtual contexts to begin with).  Setting the command-line flag will
force-enable virtual contexts on any architecture.

BUG=160710, 165531
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=172535

[aelias_OOO_until_Jul13, 2012-12-12 02:52:36]

Hi Alastair,

We figured we should turn it on for IMG only as we work out all the bugs with
the other architectures.  This will solve the performance and stability problems
with IMG.

[apatrick_chromium, 2012-12-12 02:58:58]

lgtm

[commit-bot: I haz the power, 2012-12-12 03:03:17]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/aelias@chromium.org/11555010/1

[commit-bot: I haz the power, 2012-12-12 03:14:39]

Step "update" is always a major failure.
Look at the try server FAQ for more details.

[commit-bot: I haz the power, 2012-12-12 04:16:41]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/aelias@chromium.org/11555010/1

[commit-bot: I haz the power, 2012-12-12 05:31:03]

Change committed as 172535