This patch reshuffles the colors used for the various tick categories in
the visualization. Category rows are now light gray. The new colors are
taken from the Material palette. See screenshots on the associated bug.

This patch also labels the GC bucket as such, instead of having the same
label as uncategorized C++.

Bug: v8:6240
Change-Id: I3909a177148b98e99d63f5ec9ae02e3c6f63eb24
Reviewed-on: https://chromium-review.googlesource.com/1172139
Commit-Queue: Bret Sepulveda <bsep@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55078}