Add toJSON to some performance idls

This CL adds toJSON to the following:
* PerformanceLongTaskTiming
* PerformanceResourceTiming
* TaskAttributionTiming
* Performance within workers

Link to Intent to Implement and Ship thread:
https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/ZnXvNe_wNyk

Bug: 740094
Change-Id: I54622b9bd213fd806a9108598ccf4798c2ceffa2
Reviewed-on: https://chromium-review.googlesource.com/802019
Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Reviewed-by: Philip Jägenstedt <foolip@chromium.org>
Reviewed-by: Bo <boliu@chromium.org>
Reviewed-by: Timothy Dresser <tdresser@chromium.org>
Commit-Queue: Nicolás Peña Moreno <npm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#523532}
32 files changed