Merge 22826 - Add short circuit case for self assignment, and add virtual des...

Merge 22826 - Add short circuit case for self assignment, and add virtual destructor

Pickle is a base class of Message, which has a virtual destructor, so
it is better to have Pickle have a virtual destructor as well.

Add more defensive code in the case of self assignment.
**IF** self assignment was used, and the target was readonly,
then the existing code would have a memory fault.
I don't think this is currently possible in use cases, but
the defensize code is much better. (per suggestion from CPU
on last CL).

BUG=17027
BUG=17088
r=cpu
Review URL: http://codereview.chromium.org/159800

TBR=jar@chromium.org


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=23282

[jim.roskind, 2009-08-13 07:23:40]

LGTM