GitLab

 - remove media_scanner_unittest.html, update build rules to closure
   compile this unittest, auto-generate this unittest file.
 - fix closure type errors (the test mocks and unittest code diverged
   from the real world over time, sadly), fix or add commentary.
 - import*ScanResults => import*ScanResult, the former is undefined.
 - scanDirectory|File require a |mode| argument per the externs, so
   add it everywhere.
 - re-order the test media scan and scan result class definitions to
   follow the definition order of their extern file.
 - run the js formatter over the code.

Bug: 905931
Change-Id: I27239333e2ab2d8bc1c50c6bcade75cc2d6b6701
Reviewed-on: https://chromium-review.googlesource.com/c/1348874Reviewed-by: Stuart Langley <slangley@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610506}