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This add layout tests to ensure javascript code caching is working as
expected. This also adds virtual tests with (
--enable-features=IsolatedCodeCache --site-per-process) to test that the
isolated code cache is behaving as expected. These tests test that:
1. code cache is created on the second visit to the script
2. code cache is consumed on the third visit to the script
3. code cache for the same script resource is not reused if
requested from a different origin (for the virtual tests).

This also adds a timeout expectation for the failing tests.

Bug: chromium:879494
Change-Id: I4504da0fb0222f73bbf12e93d85e12a0717f8749
Reviewed-on: https://chromium-review.googlesource.com/c/1310173
Commit-Queue: Mythri Alle <mythria@chromium.org>
Reviewed-by: Alexei Filippov <alph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606455}