[Extensions] Update SandboxedUnpackerTests to manifest v2

Update SandboxedUnpackerTests to manifest v2 and remove the allowance
for manifest v1 extensions.

Repackage all the crx's used in the sandboxed unpacker tests.

Additionally, git doesn't allow empty directories to be added to the
repository, which appears to have caused problems with some of the
unpacked versions of these extensions (where the empty directory is
necessary for the test). Add the missing directories, and put in a
dummy readme file to appease git.

Bug: 816679
Change-Id: I7130bbe89079437b8ee9090ba120039e2dbe9672
Reviewed-on: https://chromium-review.googlesource.com/1024910
Reviewed-by: Istiaque Ahmed <lazyboy@chromium.org>
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553226}
19 files changed