GitLab

Introduce the histogram
Ash.WindowSelector.TimeBetweenActiveWindowChanges
which records the amount of time between uses
of overview mode in which the user selects a window
which was not previously active.

BUG=488180
TEST=TaskSwitchMetricsRecorderTest.VerifyTaskSwitchesFromOverviewModeAreRecorded

Review URL: https://codereview.chromium.org/1132293004

Cr-Commit-Position: refs/heads/master@{#330260}