Handle missing entries in diff.js
Merge pull request #224 from google/rsturgell

Handle missing entries in diff.js
Merge pull request #227 from google/query

Initial query implementation.
Fixing two small bugs.
Splitting out attributes by those that are interesting for queries and
those that are interesting for tooltips.
Adding a virtualized table to display the query results.
This will eventually replace the search display on the tracks panel and
be used for the console panel.