Let data URLs stay in same process in RenderFrameImpl::DecidePolicyForNavigation.
Currently, several tests in content_browsertests fail under --site-per-process when they use LoadHTML(), which times out. The reason is that LoadHTML navigates the top frame to a data URL, but RenderFrameImpl::DecidePolicyForNavigation decides that the URL should be rendered in a different process and passes back a WebNavigationPolicyIgnore. This CL tweaks the logic in DecidePolicyForNavigation to allow data URLs to stay in the same process.
BUG=417518
Review URL: https://codereview.chromium.org/
619613004
Cr-Commit-Position: refs/heads/master@{#297568}