Bug 968071 - Taken/Shoot date in image/video info not localizable

This approach let us reuse an existing string, so it can be ported to
1.3

Note that this also changes the en-US format from mm-dd-YYYY to
mm/dd/YYYY
Bug 969587 - Make customization run without ICCHelper present
Bug 969587 - Integration tests for FTU variant customization
Merge pull request #16097 from qdot/969587-variant-with-no-icc

Bug 969587 - Run variant customization with no icc
Bug 966215 - Allow make test-integration to specify TEST_FILES. r=gaye
Merge pull request #16071 from flodolo/bug968071_mediainfo

Bug 968071 - Taken/Shoot date in image/video info not localizable
Bug 968049 - Don't try to reload a null URL when reviving crashed tabs