Pre-load the first diff in the diff viewer
Review Request #746 — Created Feb. 13, 2009 and submitted
Despite the new progressively loading diff viewer being faster, many users have commented that it feels slower. I believe this is because with the old diff viewer, people were used to waiting for the page to load, but pretty much mentally blocked that out. By the time it did load, they could see the diffs and interact with them. With the new diff viewer, the page itself loads instantly, but people see a spinner on the diffs, leaving them to feel that the page is now taking even longer to load (since the page itself has already loaded and NOW they have to wait for diffs). This change implements a trick to hopefully solve part of this misconception. We now load the first diff on the page along with the diff viewer, and progressively load all the other diffs. Users will see the diff viewer load (still faster than the older diff viewer) and see that first diff there, without seeing a spinner. They'll still see the other diffs load if they scroll down or if the first change is really small, but this should at least help with the perception issue in many cases.
All files still load fine. Commenting works, jumping around the diff viewer works. I haven't seen any regressions from this change.