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The purpose of this change is to provide analytics about the various
stages of the install flow. Recorded information does not contain
user-, device-, or package/app-identifying information.

Examples of recorded information are:
* duration of the flow (start to finish)
* duration of the flow until the moment the user clicks Install
* whether the attempt is an update or a new install.
* whether app verification is enabled.
* whether Unknown Sources is enabled.
* whether the attempt was blocked by Unknown Sources.
* whether permissions were displayed.
* error code (if any) returned by PackageManager when installing the
  package.

Bug: 10605940

Change-Id: I9bc009223a365a558cdf02bd91cf4315b82564c2