Revert of DevTools: notify backend agents about profiler started/stopped events

Revert of DevTools: notify backend agents about profiler started/stopped events (https://codereview.chromium.org/321173002/)

Reason for revert:
We came to the conclusion that this patch
moves us in a wrong direction. 
With this approach we would have to manage 4 pairs of states. Disabled+stopped, disabled+started, enabled+stopped, etc up to enabled+started :)
in the each agent. So we would like to try the simplest one, just use enable/disable states and fix the problems related to them.

Original issue's description:
> DevTools: notify backend agents about profiler started/stopped events
> 
> This patch provides a way to notify backend agents about starting a profiler.
> Each agent should switch to a mode which doesn't affect the performance.
> As example DebuggerAgent needs to disable breakpoints, allow v8 optimizations, etc.
> DOM and Network agents may simple disable themselves.
> 
> BUG=381115
> R=pfeldman@chromium.org
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=175946

TBR=pfeldman@chromium.org,vsevik@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=381115
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=175954

[loislo, 2014-06-11 12:17:02]

Created Revert of DevTools: notify backend agents about profiler started/stopped
events

[commit-bot: I haz the power, 2014-06-11 12:17:43]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/loislo@chromium.org/327203002/1

[commit-bot: I haz the power, 2014-06-11 12:18:41]

Change committed as 175954