Assert that thread-safe reference counting is used with...

Assert that thread-safe reference counting is used with
cross-thread NewRunnableMethod.

This assertion caught such an error in VisitedLinkMaster!

My approach, modify RunnableMethodTraits<T> to assert that
when ReleaseCallee happens on a different thread from
RetainCallee that the type supports thread-safe reference
counting.  I do this by adding a static method to both
RefCounted<T> and RefCountedThreadSafe<T>.

This results in a little ugliness in cases where people
implement AddRef and Release by hand (to make the no-ops).
There may be a nicer way to deal with those few cases.

R=brettw
BUG=none
TEST=none


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=27379

[brettw, 2009-09-28 17:38:05]

I think this is a really good solution. LGTM