Revert of Pepper: Clean up ProgressEvent logic.

Revert of Pepper: Clean up ProgressEvent logic. (https://codereview.chromium.org/270453004/)

Reason for revert:
This broke our app. We do not understand why the breakage happened or
why browser_tests could not catch this yet. However, as our app do not
want this in M36, I'd revert this change without checking.

BUG=372163
Original issue's description:
> Pepper: Clean up ProgressEvent logic.
> 
> This simplifies NexeLoadManager, which is getting pretty big. This also removes
> an unused field from ProgressEvent, and adds a convenience function for posting
> a task to dispatch a progress event from the main thread, which is often
> necessary to ensure that progress events are posted to the DOM after other
> state changes.
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=269362

TBR=dmichael@chromium.org,teravest@chromium.org
NOTREECHECKS=true
NOTRY=true

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=269747

[hamaji, 2014-05-12 07:11:56]

Created Revert of Pepper: Clean up ProgressEvent logic.

[commit-bot: I haz the power, 2014-05-12 07:12:04]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/hamaji@chromium.org/275403004/1

[commit-bot: I haz the power, 2014-05-12 07:12:55]

Change committed as 269747

[teravest, 2014-05-12 14:04:54]

lgtm