Fix memory leak in corrupt JPEG decoding.

Fix memory leak in corrupt JPEG decoding.

BUG=10945
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=16352

[Lei Zhang, 2009-05-15 00:11:03]

"gotcha!" (it wasn't obvious because it was in an error handler)

[Lei Zhang, 2009-05-15 21:26:49]

Upon closer look, this is happening because we're in undefined behavior
territory. From man longjmp:

The values of automatic variables are unspecified after a call to longjmp() if
they meet all the following criteria:

- they are local to the function that made the corresponding setjmp(3) call;
- their values are changed between the calls to setjmp(3) and longjmp(); and
- they are not declared as volatile.

The destroyer variable met all 3 criterias, so cinfo_ was mysteriously getting
set to 0, thus it wasn't getting freed in DestroyManagedObject();

[dank, 2009-05-19 00:35:56]

LGTM, though I couldn't tell at first glance whether the
rest of the function is safe.  (I wonder if one shouldn't
avoid using local variables in the same function as longjmp
alltogether... or mark them all volatile.)