Use the DrmDeviceManager to get the primary device in GbmSurfaceFactory

Use the DrmDeviceManager to get the primary device in GbmSurfaceFactory

Remove the requirement of a GBM device at construction time for
GbmSurfaceFactory and switch to using EGL_DEFAULT_DISPLAY as a native
display.

This allows us to remove the hacks to open the "primary" graphics device
in the GPU initialization. Graphics device initialization would be fully
handled via hotplugging.

BUG=427959
Committed: https://crrev.com/051001f2edf52d64239f5afc3ac68d9153ec2470
Cr-Commit-Position: refs/heads/master@{#318057}

[dnicoara, 2015-02-25 15:15:08]

dnicoara@chromium.org changed reviewers:
+ alexst@chromium.org

[dnicoara, 2015-02-25 15:15:09]

PTAL

[alexst (slow to review), 2015-02-25 15:25:28]

lgtm

[dnicoara, 2015-02-25 16:23:53]

The CQ bit was checked by dnicoara@chromium.org

[commit-bot: I haz the power, 2015-02-25 16:25:11]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/955013002/1

[commit-bot: I haz the power, 2015-02-25 16:27:55]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-25 16:28:56]

Patchset 1 (id:??) landed as
https://crrev.com/051001f2edf52d64239f5afc3ac68d9153ec2470
Cr-Commit-Position: refs/heads/master@{#318057}

[vignatti (out of this project), 2015-02-26 21:16:04]

dnicoara@ this exact CL is breaking my system -- any idea how I can help to
track down the issue? This is ozone_demo's bt:

https://gist.githubusercontent.com/tiagovignatti/2e2db754472792c51387/raw/02c...