Report the apptest fixture name for isolated fixture crashes.
Report the apptest fixture name for isolated fixture crashes.

Report specific Suite.Fixture crashes instead of mojo:foo_apptest.
Better than reporting 'mojo:foo_apptests' for each of 10 fixtures, eg.:
http://build.chromium.org/p/chromium.mojo/builders/Chromium%20Mojo%20Windows/builds/58/steps/app_tests/logs/stdio

TODO: Similar reporting (and avoid crashing fixtures) when not isolated.

BUG=509880
TEST=Better logging for apptest crashes on isolated fixtures.
R=sky@chromium.org

Review URL: https://codereview.chromium.org/1275123002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#342228}

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