Fix proxy_connection tests for M74

There is some difference with M74 and M75, that the
WarmupURLFetcherCallback.SuccessfulFetch.*.Core is recorded in M75 and
*.NonCore. The test is fixed to expect on any of the histograms.

Also fixes a logic typo in video test.

Bug: 964156
Change-Id: I5408b10cac26dc616980177bdbd317e3e90a3da9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1617202
Commit-Queue: rajendrant <rajendrant@chromium.org>
Reviewed-by: Robert Ogden <robertogden@chromium.org>
Cr-Commit-Position: refs/heads/master@{#660906}