Remove some confusing code from ToplevelWindowEventHandler::HandleMousePressed()

ToplevelWindowEventHandler::HandleMousePressed() has some comments about only handling events post target. Those comments are untrue so remove them.
It is also non trivial to get the originally desired behavior, namely getting mouse events to HTML elements with the "-webkit-app-region" CSS style applied. 

BUG=None
TEST=None

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=243439

[pkotwicz, 2013-12-25 02:30:15]

Ben can you please take a look?
I think you initially added this code to allow HTML elements with
-webkit-app-region to intercept mouse events.
It is non trivial to get that behavior. Namely:
- We would need to stop always settings events as handled in
RenderWidgetHostViewAura::OnMouseEvent()
- We would need to fix this functionality on OSes other than CrOS (It does not
work on Windows or Linux GTK, have not checked Mac)
- There is probably more important functionality to implement

Does it make sense to make ToplevelWindowEventHandler only a pre target handler
once more?

[Ben Goodger (Google), 2014-01-06 17:50:32]

lgtm

[commit-bot: I haz the power, 2014-01-07 09:52:27]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/pkotwicz@chromium.org/108723008/30001

[commit-bot: I haz the power, 2014-01-07 12:09:17]

Retried try job too often on win_rel for step(s) browser_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_rel&nu...

[commit-bot: I haz the power, 2014-01-07 16:36:18]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/pkotwicz@chromium.org/108723008/30001

[commit-bot: I haz the power, 2014-01-07 19:56:23]

Retried try job too often on win_rel for step(s) nacl_integration
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_rel&nu...

[commit-bot: I haz the power, 2014-01-07 21:13:06]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/pkotwicz@chromium.org/108723008/30001

[commit-bot: I haz the power, 2014-01-08 00:09:34]

Change committed as 243439