cc: Add debug info for unexpected SwapBuffersComplete

cc: Add debug info for unexpected SwapBuffersComplete

Unexpected SwapBuffersComplete's can arrive for two common reasons:
1) DidSwapBuffersComplete is getting called before DidSwapBuffers.
2) A swap ack from the previous OutputSurface arrives.

This extra debug info will allow us to determine which case
we are in.

BUG=495650
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Committed: https://crrev.com/1545de0e093bbd38d12c69ea602b5141356a647e
Cr-Commit-Position: refs/heads/master@{#333148}

[brianderson, 2015-06-05 18:03:07]

brianderson@chromium.org changed reviewers:
+ sunnyps@chromium.org

[brianderson, 2015-06-05 18:03:08]

ptal!

[sunnyps, 2015-06-05 20:43:02]

LGTM

[brianderson, 2015-06-05 20:49:09]

The CQ bit was checked by brianderson@chromium.org

[commit-bot: I haz the power, 2015-06-05 20:52:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1153283009/1

[commit-bot: I haz the power, 2015-06-05 22:05:53]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-05 22:06:57]

Patchset 1 (id:??) landed as
https://crrev.com/1545de0e093bbd38d12c69ea602b5141356a647e
Cr-Commit-Position: refs/heads/master@{#333148}