Keep the module in scope when executing scripts. This prevents a crash when the

Keep the module in scope when executing scripts. This prevents a crash when the
script deletes the plugin object synchronously. This in turn deletes the
dispatcher which will make the code returning the out param and exception to
the plugin crash.

To prevent the crash, this patch adds a way for the proxy to manipulate the
refcount of the plugin object so that it's still alive when as long as the
scripting message is being processed.

A manual test is included. This is not automatically run now. I tried to fit it
into the current test infrastructure and found it very challenging, We need to
revisit this to allow custom tests to more easily be written.

TEST=manual with included plugin and html
BUG=none
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=81993

[viettrungluu, 2011-04-18 19:53:41]

LGTM w/nits.

http://codereview.chromium.org/6881012/diff/5003/ppapi/proxy/host_dispatcher.cc
File ppapi/proxy/host_dispatcher.cc (right):

http://codereview.chromium.org/6881012/diff/5003/ppapi/proxy/host_dispatcher....
ppapi/proxy/host_dispatcher.cc:236: 
Nit: Is the extra blank line really necessary?

http://codereview.chromium.org/6881012/diff/5003/ppapi/tests/manual/delete_pl...
File ppapi/tests/manual/delete_plugin.cc (right):

http://codereview.chromium.org/6881012/diff/5003/ppapi/tests/manual/delete_pl...
ppapi/tests/manual/delete_plugin.cc:45: /*
Could you add a comment on why it's commented out?