Render process changes for ResourceTiming sizes.

This is part of the changes to add the size fields to the
PerformanceResourceTiming API.

Intent to ship: https://groups.google.com/a/chromium.org/d/msg/blink-dev/1bdP80f0GVs/U7qIckr-BQAJ

These are the render process changes which take the "encodedBodySize" and
"transferSize" fields that were received from the browser and make them
available on the PerformanceResourceTiming object.

In addition, code is added to track the "decodedBodySize" by summing all the
data bytes that are read from the browser process, and this is also made
available on the PerformanceResourceTiming object.

See the design doc at
https://docs.google.com/document/d/1ckL-rKLFRsdI4nn1golvQ6I1zRIvxgFkDXMrZb8KduY/edit
for a far more detailed description of the changes.

BUG=467945
TBR=liberato

Review-Url: https://codereview.chromium.org/2105713002
Cr-Commit-Position: refs/heads/master@{#406527}
86 files changed