HomeFragment is unexpectedly inflated on cold VIEW start up (was: 39-127ms COLD VIEW start up regression around 10/1)

[mcomella]

This is a breakout from #21749.

We see a regression between 9/29 and 10/1:

• VIEW: 39ms

The regression continues to rise. From 9/29 to 10/5, we see a regression of:

• VIEW: 127ms

VIEW (note the scales are different):

This seems like it could be be two discrete regressions – one between 9/29 & 10/1 and one on 10/5. Dashboard link. The numbers seem a little noisy so let me know if you think it's worth retaking them. Maybe we should start with a profile though.

Profiles

VIEW:

• 9/29 VIEW: https://share.firefox.dev/2YoJS2W
• 10/5 VIEW: https://share.firefox.dev/3uUxbcn

One notable visual difference between these builds is the inclusion of Pocket content. There was also an update the synchronized the layouts for the homescreen. These could be the two events I mentioned above. However, this shouldn't affect the VIEW code path: let's find out what's going on.

┆Issue is synchronized with this Jira Task

[csadilek]

What we're seeing here is that the execution time of HomeFragment.onCreateView increased, which makes sense given that we added a lot of features to it recently. However, we shouldn't have to create this view to begin with, as the intention here is to launch into a tab.

[mcomella]

The day after the PR #21805 landed, we measured an improvement of ~138ms to our COLD VIEW start up numbers. 🎉 This is similar to what I measured in my proof-of-concept measuring; #21805 (comment)