Wait at least XXX ms before showing the loading content screen

Otherwise, the user just thinks the conversation is delayed for no
good reason.
May want to tweak number a bit, but its def better
hopefully, we can make this a bit smoother, too
gets janky when some parts of the webview/ header load before the conversation loads
May be able to add a scrim to block the visible jank, but the 3 layers in the conversation
view are making this a bit tricky
Fixes b/7133753 don't show loading progress view for conversation until XXX ms have passed

Change-Id: If141ff4c07de92ad3dadd15ff003d64d557a5ea4
2 files changed