Reenable data URL layout tests which were temporarily skipped until Chromium side change gets landed

- Enables the temporarily skipped tests
- Change the blob test case to expect failure. This is because it turned
  out that we cannot use the optimization for data URL loading when XHR
  is set to load data as Blob.
- Delete the unnecessary expectation file

Depends on
- https://codereview.chromium.org/480413007/
- https://codereview.chromium.org/294193002/

BUG=308768

Review URL: https://codereview.chromium.org/492183002

git-svn-id: svn://svn.chromium.org/blink/trunk@181707 bbb929c8-8fbe-4397-9dbb-9b2b20218538