Enable movement between class/package visualizations using URLs

Node has been specialized into {Package, Class}Node containing metadata
specific to each type of graph. A new component has also been added to
each page:

* A URL on the class graph leading back to the selected class' package
* A set of URLs on the package graph containing:
  * Links to the class graph for each of the selected package's classes
  * A link to the class graph for all of the selected package's classes

This allows UI-based movement between the different types of graphs.

Bug: 1093962
Change-Id: I3925eb3c02bd6d09ecdba60d57b5dae908c24358
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2288949
Commit-Queue: James Long <yjlong@google.com>
Reviewed-by: Samuel Huang <huangs@chromium.org>
Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#787220}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 52f5cb1151c679fc8678f3343589a33d62da124c
13 files changed