Closure compile multi_metadata_provider_unittest

 - remove multi_metadata_provider_unittest.html
 - add BUILD rules to auto-generate and compile this unittest
 - fix Closure compiler errors.

No change in test behavior.

Bug: 913294
Change-Id: I97f20c329f6ba89e0f4580be8d1e52f68331fe25
Reviewed-on: https://chromium-review.googlesource.com/c/1368856
Reviewed-by: Stuart Langley <slangley@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#615029}
4 files changed