Reland "Prevent liveedit on or under generators with open activations"

Reland "Prevent liveedit on or under generators with open activations"

The change relative to the previous CL is a logic change in
DropActivationsInActiveThreadImpl.  The previous CL skipped the matcher
unless the frame was a JS frame; this was correct for
MultipleFunctionTarget but not for SingleFrameTarget.

I have not been able to reproduce the original failures on either
architecture (ia32 or x64; stack frame dropping is unsupported on other
architectures).

R=yangguo@chromium.org
LOG=N
TEST=mjsunit/harmony/generators-debug-liveedit.js
BUG=

Committed: https://code.google.com/p/v8/source/detail?r=21419

[wingo, 2014-05-07 09:55:08]

I would appreciate help in reproducing the original failure; otherwise we can
just throw it at the buildbot and see what happens.

Is there something incompatible with creating a handle scope while in a
DisallowHeapAllocation and iterating the heap, perhaps?  (Thinking out loud as
to possibilities for the original failure.)

[Yang, 2014-05-20 14:55:59]

On 2014/05/07 09:55:08, wingo wrote:
> I would appreciate help in reproducing the original failure; otherwise we can
> just throw it at the buildbot and see what happens.
> 
> Is there something incompatible with creating a handle scope while in a
> DisallowHeapAllocation and iterating the heap, perhaps?  (Thinking out loud as
> to possibilities for the original failure.)

I can't figure out what went wrong. Let's just recommit and see what happens :)
lgtm.

[Yang, 2014-05-22 07:33:08]

Committed patchset #1 manually as r21419 (presubmit successful).