android: Allow Paint Preview to happen with native

The decision whether to display the Paint Preview depends on the
heuristic detecting cold start: the start is considered _not_ cold (i.e.
warm) when the native library has already been loaded and initialized.

We hypothesize that recently the library started becoming initialized
very early in the process lifetime. One of the causes for it is
asynchronous library loading on a separate thread.

As a result of recent changes, the volume of UMA samples for
"Browser.PaintPreview.TabbedPlayer.TimeToFirstBitmap" has dropped
dramatically, leading to Paint Preview becoming less useful.

This change attempts to use another heuristic for a cold start:
1. the app process creation is caused by an activity
2. no activity is paused prior to pre-inflation of the tabbed activity

The (1) uses a new "process creation reason" trick available on P+
devices and falls back to time-based detection for older devices.

Bug: 1471136
Change-Id: I3cdd6adc13212890619b2242ce2bfadd0d23fa3f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4874028
Reviewed-by: Michael Thiessen <mthiesse@chromium.org>
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Commit-Queue: Egor Pasko <pasko@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1204729}