Fix queuing of display power state change requests

Fix queuing of display power state change requests

If a display power change request arrives before the previous one
finishes or if a previous power change request failed the state becomes
inconsistent and future requests are optimized out.

BUG=627795
TEST=New unittest in display_unittests and manually checked on Samus

Review-Url: https://codereview.chromium.org/2154743003
Cr-Commit-Position: refs/heads/master@{#405990}
(cherry picked from commit 760bfbf595eb8e4597c971b60c2da1c911481fbd)

Committed: https://chromium.googlesource.com/chromium/src/+/e3b52ec90617f1fc68328068c959e28f2ee23353

[dnicoara, 2016-07-21 15:26:33]

Description was changed from

==========
Fix queuing of display power state change requests

If a display power change request arrives before the previous one
finishes or if a previous power change request failed the state becomes
inconsistent and future requests are optimized out.

BUG=627795
TEST=New unittest in display_unittests and manually checked on Samus

Review-Url: https://codereview.chromium.org/2154743003
Cr-Commit-Position: refs/heads/master@{#405990}
(cherry picked from commit 760bfbf595eb8e4597c971b60c2da1c911481fbd)
==========

to

==========
Fix queuing of display power state change requests

If a display power change request arrives before the previous one
finishes or if a previous power change request failed the state becomes
inconsistent and future requests are optimized out.

BUG=627795
TEST=New unittest in display_unittests and manually checked on Samus

Review-Url: https://codereview.chromium.org/2154743003
Cr-Commit-Position: refs/heads/master@{#405990}
(cherry picked from commit 760bfbf595eb8e4597c971b60c2da1c911481fbd)

Committed:
https://chromium.googlesource.com/chromium/src/+/e3b52ec90617f1fc68328068c959...
==========

[dnicoara, 2016-07-21 15:26:34]

Committed patchset #1 (id:1) manually as
e3b52ec90617f1fc68328068c959e28f2ee23353.