Now that we have moved some about: pages to the privileged content process,
opening these URLs from a non-privileged content process will trigger SessionStore
to restore the tab state due to a process flip. We will set favicons for these
URLs earlier to avoid flickering and improve perceived performance.
This patch also prevents the spinner whenever a page with a local about: URI
(about:blank and about: pages that resolve to jar:// or file:// URIs) is
loaded from a process that the URI cannot load in (e.g. loading about:newtab
in the web content process), as well as during tab duplication or session
restoration for such local about: URIs.
Before this patch, there were additional frames when opening a new window, causing
browser/base/content/test/performance/browser_windowopen.js to fail. This patch
will reduce the number of frames when opening a new window.
MozReview-Commit-ID: yjj2964KSz
a0680e88ae