Bug 987496 - Adding Hindi Input Method for B2G

Cherry-pick from 7882bd086a460ff07b170ed45a1cf8981f4d0f72

Conflicts:

	build/config/keyboard-layouts.json
Merge pull request #22901 from nullaus/v1.4

Merge pull request #22799 from nullaus/bug1049790
Bug 1044960 - hide startscreen if tab url was null
Merge pull request #22762 from luke-chang/987496_v1.4_hindi_input_method

Bug 987496 - Adding Hindi Input Method for B2G
Revert "Merge pull request #22762 from luke-chang/987496_v1.4_hindi_input_method"

This reverts commit 6572583f91a3937839b1ff5c7d370b6a11a34c24, reversing
changes made to 93b469e3643f6caed8e190c72b612c60f6a74a1e.
Bug 1044960 - fix lint error, r=me
Revert "Merge pull request #22901 from nullaus/v1.4"

This reverts commit ab9a57d204c8c06cccc70cb7190da789fe17a3cb, reversing
changes made to 518c6afa28dc3b87e3a7360ee4b751885884d03d.
Merge pull request #22945 from nullaus/bug1053509

bug 1053509 - Use plain js download object when download succeeds. r=crd...
(cherry picked from commit 385f8b1fc9179441c9d6a6ad16ff8701edfa1faa)