Turn on default SiteInstance by default.

- Enable default SiteInstance by default so Android will start using
  fewer processes for sites that do not need isolation.
- Fixed a test that was accidentally broken by the fix in
  http://crrev.com/c/1717194 .

Bug: 787576
Change-Id: Icb2d6cd28e51945fb85ddb48f99a9183e1d582b0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1722982
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Commit-Queue: Aaron Colwell <acolwell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#681997}
2 files changed