Introduce MaybeHandle to police exception checking in handlified code.

Introduce MaybeHandle to police exception checking in handlified code.

R=ishell@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=20457

[Yang, 2014-04-02 13:07:48]

Please take a look.

[Michael Starzinger, 2014-04-02 14:24:46]

Drive-by comments.

https://codereview.chromium.org/222163002/diff/20001/src/handles.h
File src/handles.h (right):

https://codereview.chromium.org/222163002/diff/20001/src/handles.h#newcode38
src/handles.h:38: class MaybeHandle {
Can we get a few comments above this class about why we have it and what
distinguishes it from an ordinary Handle?

https://codereview.chromium.org/222163002/diff/20001/src/handles.h#newcode94
src/handles.h:94: INLINE(Handle()) {}
As discussed offline: The ultimate goal of this endeavor is to get rid of this
constructor. I totally understand that this will take some time, but can we
leave a TODO here in that regard? Without reaching this goal, all the changes
leading up to it would increase complexity instead of reducing it.

https://codereview.chromium.org/222163002/diff/20001/src/handles.h#newcode124
src/handles.h:124: static Handle<T> null() { return Handle<T>(); }
Likewise.

[Toon Verwaest, 2014-04-02 14:40:24]

drive-by-comment

https://codereview.chromium.org/222163002/diff/20001/src/handles.h
File src/handles.h (right):

https://codereview.chromium.org/222163002/diff/20001/src/handles.h#newcode88
src/handles.h:88: class Handle : public MaybeHandle<T> {
I find it pretty confusing that a "checked handle" is an "unchecked handle".

[Igor Sheludko, 2014-04-02 15:25:25]

lgtm

https://codereview.chromium.org/222163002/diff/100001/src/handles.h
File src/handles.h (right):

https://codereview.chromium.org/222163002/diff/100001/src/handles.h#newcode108
src/handles.h:108: INLINE(Handle()) : location_(NULL)  {}
Extra space before {}

[Yang, 2014-04-03 05:57:51]

Committed patchset #7 manually as r20457 (presubmit successful).