Merge 188631 "Don't throw exceptions when v8 objects/contexts ar..."

Merge 188631 "Don't throw exceptions when v8 objects/contexts ar..."

> Don't throw exceptions when v8 objects/contexts are missing, and catch
> exceptions that are thrown on GC. There is a path crashing the renderer:
> v8 GC -> run extension function -> throws exception -> webkit tries to log ->
> context has been GCed -> crash. Try to avoid that.
> 
> 
> BUG=196581
> R=mpcomplete@chromium.org
> TBR=jhawkins@chromium.org
> 
> Review URL: https://chromiumcodereview.appspot.com/12853007

TBR=kalman@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=188638

[kareng, 2013-03-17 14:02:51]

Committed patchset #1 manually as r188638.