Group log messages by page_id on chrome://interventions-internals.

Decision log messages are grouped so that they don't flood the logs
table.

Log messages can be grouped by page_id retrieved from PreviewsIOData.  The
messages that don't need grouping can use 0 as page_id, since the generated IDs
start at 1.

Screenshot: https://drive.google.com/a/chromium.org/file/d/17mp8fIHWIJjbZp_t711PGLEaWuZoG1v2
Screenshot: https://drive.google.com/a/chromium.org/file/d/1KI_f1XCYVSk2hLqq2LGaTr0g7LZ6oQcd

Bug: 791637
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I5eff89d6a8ffc38209819d8787fdac30caaa939a
Reviewed-on: https://chromium-review.googlesource.com/806758
Reviewed-by: Ryan Sturm <[email protected]>
Reviewed-by: Tarun Bansal <[email protected]>
Reviewed-by: Tom Sepez <[email protected]>
Commit-Queue: Thanh Le <[email protected]>
Cr-Commit-Position: refs/heads/master@{#522187}
17 files changed