GTTF: Include info about disabled tests and platforms in JSON test summary.

This will make it possible to analyze which tests are disabled on specific
platforms, and whether the failures are really platform-specific.

Including list of all tests in the summary makes it possible to e.g. detect
when a test first appeared (or disappeared), which platforms a test is compiled
on, or whether some tests have been filtered out.

BUG=236893
R=sky@chromium.org

Review URL: https://codereview.chromium.org/93603008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243232 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 243232