Fix test suite proxiesAvailableToTamingCode condition. https://codereview.appspot.com/12675043
Fix test suite proxiesAvailableToTamingCode condition.
https://codereview.appspot.com/12675043

Due to WeakMap implementation we sometimes delete Proxy from the SES
frame, so testing for Proxy in the host frame is not a suitable test.
Get the actual SES frame instead.

This fixes a bogus test failure on current Chrome Beta w/ Experimental
JavaScript flag enabled.

R=felix8a@gmail.com


git-svn-id: eb21526166532bd3afc2c1499c0cf105ce815f5a@5541 360991c0-9f3b-0410-ba87-8b362a00edf4

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