Add Persistent::ClearAndLeak.

Add Persistent::ClearAndLeak.

This will be relevant after Persistent is changed to Dispose itself when
destructed. With Persistent::ClearAndLeak, Blink can take the ownership of the
object pointed by a Persistent and avoid it getting destructed.

BUG=
R=svenpanne@chromium.org

Committed: http://code.google.com/p/v8/source/detail?r=14624

[marja, 2013-05-10 10:34:52]

svenpanne, ptal

[Sven Panne, 2013-05-10 12:00:02]

lgtm

https://codereview.chromium.org/15023010/diff/1/include/v8.h
File include/v8.h (right):

https://codereview.chromium.org/15023010/diff/1/include/v8.h#newcode698
include/v8.h:698: V8_INLINE(T* LeakPersistent());
Please add a comment that it is necessary to re-wrap the pointer later and
Dispose it, otherwise one keeps a Node live indefinitely.

https://codereview.chromium.org/15023010/diff/1/include/v8.h#newcode5408
include/v8.h:5408: T* Persistent<T>::LeakPersistent() {
As discussed offline, we should better name it "ClearAndLeak".

https://codereview.chromium.org/15023010/diff/1/include/v8.h#newcode5411
include/v8.h:5411: old = this->operator*();
Can we use '*this' here? If not, a comment might be good...

[marja, 2013-05-10 13:02:25]

Thanks for review!

https://codereview.chromium.org/15023010/diff/1/include/v8.h
File include/v8.h (right):

https://codereview.chromium.org/15023010/diff/1/include/v8.h#newcode698
include/v8.h:698: V8_INLINE(T* LeakPersistent());
On 2013/05/10 12:00:02, Sven Panne wrote:
> Please add a comment that it is necessary to re-wrap the pointer later and
> Dispose it, otherwise one keeps a Node live indefinitely.

Done.

https://codereview.chromium.org/15023010/diff/1/include/v8.h#newcode5408
include/v8.h:5408: T* Persistent<T>::LeakPersistent() {
On 2013/05/10 12:00:02, Sven Panne wrote:
> As discussed offline, we should better name it "ClearAndLeak".

Done.

https://codereview.chromium.org/15023010/diff/1/include/v8.h#newcode5411
include/v8.h:5411: old = this->operator*();
On 2013/05/10 12:00:02, Sven Panne wrote:
> Can we use '*this' here? If not, a comment might be good...

"this" is not Persistent, but Persistent*, so "*this" won't be the right thing.
But we can use "**this". It's just not very clear. (Changed to **this, however.)

[Sven Panne, 2013-05-10 13:06:57]

lgtm

[Michael Starzinger, 2013-05-10 14:04:58]

Committed patchset #2 manually as r14624 (presubmit successful).