GitLab

- PrintRenderFrameHelperTest.WindowPrintBeforePrintAfterPrint covers the
  regression in bug 912966 without Print Preview.
- PrintRenderFrameHelperPreviewTest.WindowPrintBeforePrintAfterPrint
  covers the regression in bug 912966 with Print Preview.
- PrintRenderFrameHelperPreviewTest.BasicBeforePrintAfterPrint is the
  equivalent to PrintRenderFrameHelperTest.BasicBeforePrintAfterPrint,
  but for Print Preview.
- Merge common code to avoid repeats.

BUG=912966

Change-Id: I80b0ef718e4f06e2e1bd858bd1c2a39028d4a6ec
Reviewed-on: https://chromium-review.googlesource.com/c/1371211
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#615624}