Revert of Use ScopedPersistent for persistent handles in V8PerContextData (https://codereview.chromium.org/149263005/)

Reason for revert:
This change is being blamed for many virtual/threaded/transitions timeouts on the bots. There is no obvious connection between these test timeouts and this patch, but this is the only change listed when the timeouts started to occur.

Some of the timeouts: http://goo.gl/6tX16t

Original issue's description:
> Use ScopedPersistent for persistent handles in V8PerContextData
> 
> Using ScopedPersistent is safer, since ScopedPersistent will be automaticallly
> destructed when the scope is exited.
> 
> (Another motivation is that I want to replace all raw persistent handles
> with ScopedPersistent/UnsafePersistent in order to verify that persistent
> handles don't leak among worlds.)
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=166569

TBR=jochen@chromium.org,dcarney@chromium.org,haraken@chromium.org
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/150283006

git-svn-id: svn://svn.chromium.org/blink/trunk@166577 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Revert of Revert of Use ScopedPersistent for persistent handles in V8PerContextData (https://codereview.chromium.org/150283006/)

Reason for revert:
Haraken's original patch (https://src.chromium.org/viewvc/blink?view=rev&revision=166569) did not cause the timeouts we thought it did. I am relanding the patch that was incorrectly reverted.

Original issue's description:
> Revert of Use ScopedPersistent for persistent handles in V8PerContextData (https://codereview.chromium.org/149263005/)
> 
> Reason for revert:
> This change is being blamed for many virtual/threaded/transitions timeouts on the bots. There is no obvious connection between these test timeouts and this patch, but this is the only change listed when the timeouts started to occur.
> 
> Some of the timeouts: http://goo.gl/6tX16t
> 
> Original issue's description:
> > Use ScopedPersistent for persistent handles in V8PerContextData
> > 
> > Using ScopedPersistent is safer, since ScopedPersistent will be automaticallly
> > destructed when the scope is exited.
> > 
> > (Another motivation is that I want to replace all raw persistent handles
> > with ScopedPersistent/UnsafePersistent in order to verify that persistent
> > handles don't leak among worlds.)
> > 
> > Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=166569
> 
> TBR=jochen@chromium.org,dcarney@chromium.org,haraken@chromium.org
> NOTREECHECKS=true
> NOTRY=true
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=166577

TBR=jochen@chromium.org,dcarney@chromium.org,haraken@chromium.org
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/137213006

git-svn-id: svn://svn.chromium.org/blink/trunk@166578 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Revert of Revert of Web Animations: Replace hasIterationDuration with a NaN duration value (https://codereview.chromium.org/144233009/)

Reason for revert:
Tim's original patch (https://src.chromium.org/viewvc/blink?view=rev&revision=166567) did not cause the timeouts we thought it did. I am relanding the patch that was incorrectly reverted.

Original issue's description:
> Revert of Web Animations: Replace hasIterationDuration with a NaN duration value (https://codereview.chromium.org/154333003/)
> 
> Reason for revert:
> Several virtual/threaded/transitions just started timing out and I suspect this patch may be the cause. A sample is below:
> http://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=virtual%2Fthreaded%2Ftransitions%2Ftransition-end-event-rendering.html
> 
> Original issue's description:
> > Web Animations: Replace hasIterationDuration with a NaN duration value
> > 
> > Minor clean-up to the code; e.g. this makes writing tests a bit simpler.
> > 
> > BUG=335350
> > 
> > Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=166567
> 
> TBR=dstockwell@chromium.org,timloh@chromium.org
> NOTREECHECKS=true
> NOTRY=true
> BUG=335350
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=166575

TBR=dstockwell@chromium.org,timloh@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=335350

Review URL: https://codereview.chromium.org/142383004

git-svn-id: svn://svn.chromium.org/blink/trunk@166579 bbb929c8-8fbe-4397-9dbb-9b2b20218538