Activate the use of is_unexpected field in the output JSON file.

Check in bits of code from the pending two-way sync CL. It allows me to monitor the flakiness of webdriver_test_suit on Linux Tests (dbg)(1) while the other CL is being reviewed. The changes are taken from https://chromium-review.googlesource.com/c/chromium/src/+/1484616/36

Sample JSON output:
https://pastebin.com/CfuVTuP8

The is_unexpected fields for all of the three tests are false because their expectations exist in the WebDriverExpectations.

Bug: 934919
Change-Id: If068f2318f2f2cbe6b866f96f14cb97f941a4df0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1574360
Reviewed-by: John Chen <johnchen@chromium.org>
Reviewed-by: Robert Ma <robertma@chromium.org>
Commit-Queue: Kyle Ju <kyleju@chromium.org>
Cr-Commit-Position: refs/heads/master@{#652292}
4 files changed