[Extensions] Update ExtensionIconSourceTests to manifest v2

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

Bug: 816679
Change-Id: I6fe638994b9ca34b03fc16debcfb547d75e967e1
Reviewed-on: https://chromium-review.googlesource.com/1018405
Reviewed-by: Istiaque Ahmed <lazyboy@chromium.org>
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#552093}
1 file changed