Use iframe in blink_perf.pywebsocket perf tests to remove --disable-web-security

Previously:
(a) util_performance_test.js in Blink runs performance tests using
(b) pywebsocket's scripts,
but this required --disable-web-security for cross-origin workers
because (a) and (b) have different origins.

We change this so that:
(a) util_performance_test.js creates
(c) <iframe> with src=pywebsocket's example/*_iframe.html that runs
    the performance tests on the iframe using
(b) pywebsocket's scripts.
Because (b) and (c) have the same origin (but (a) has a different origin),
Tests are run in the same-origin while we have an cross-origin iframe.

This CL adds pywebsocket-side iframe HTML/JavaScript files for (b) and (c). and
updates DEPS to include pywebsocket-side changes [1].

[1] pywebsocket-side: https://github.com/google/pywebsocket/pull/147
[2] Chromium-side: This CL.
BUG=567533
CQ_EXTRA_TRYBOTS=tryserver.chromium.perf:linux_perf_bisect;tryserver.chromium.perf:mac_10_10_perf_bisect;tryserver.chromium.perf:win_perf_bisect

Review URL: https://codereview.chromium.org/1521943002

Cr-Commit-Position: refs/heads/master@{#365787}
39 files changed