Make run-bindings-tests verify extended attributes
Make run-bindings-tests verify extended attributes

The file IDLAttributes.txt lists supported extended attributes so that
unknown attributes can be rejected by builds. But this file was not
being used by run-bindings-tests itself so the test files could fall
out of sync with supported syntax.

TBR=haraken@chromium.org,abarth@chromium.org

Review URL: https://codereview.chromium.org/14171010

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@148210 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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