Tentatively re-enable PhysicalResourceProviderTest.
Tentatively re-enable PhysicalResourceProviderTest.

It still might be flaky and fail sometimes.
I will observe it, and if it is, I will extract file watching into
a separate suite, marked as flaky.

R=1f7641b6b14c52b9163524ab8d9aabff80176f21@google.com, 72d414e3a99fb120308437779d51667bcc0984eb@google.com

Bug: https://github.com/dart-lang/sdk/issues/25472
Change-Id: I82eadc7976f8f813cfaa1457735dee285a12aebd
Reviewed-on: https://dart-review.googlesource.com/77229
Reviewed-by: Brian Wilkerson <1f7641b6b14c52b9163524ab8d9aabff80176f21@google.com>
Reviewed-by: Paul Berry <72d414e3a99fb120308437779d51667bcc0984eb@google.com>
Commit-Queue: Konstantin Shcheglov <09e4d7516628963212bf4aace2f97603d2b706e4@google.com>

dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk