The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5c9311ed7789a0591420b9b4b46cab5519651caa

commit 5c9311ed7789a0591420b9b4b46cab5519651caa
Author: pkotwicz <pkotwicz@chromium.org>
Date: Thu Jun 29 21:08:55 2017

Add UMA metric to track the time elapsed since a WebAPK was last launched

This CL also:
Adds a new SharedPreferences property "has_been_launched" to track whether the
WebAPK/Webapp has been launched from the home screen.

BUG= 730201 
Test=WebApkIntegrationTest.*, WebappModeTest.*

Review-Url: https://codereview.chromium.org/2930553002
Cr-Commit-Position: refs/heads/master@{#483485}

[modify] https://crrev.com/5c9311ed7789a0591420b9b4b46cab5519651caa/base/android/java/src/org/chromium/base/metrics/RecordHistogram.java
[modify] https://crrev.com/5c9311ed7789a0591420b9b4b46cab5519651caa/base/android/record_histogram.cc
[modify] https://crrev.com/5c9311ed7789a0591420b9b4b46cab5519651caa/chrome/android/java/src/org/chromium/chrome/browser/ServiceTabLauncher.java
[modify] https://crrev.com/5c9311ed7789a0591420b9b4b46cab5519651caa/chrome/android/java/src/org/chromium/chrome/browser/metrics/WebApkUma.java
[modify] https://crrev.com/5c9311ed7789a0591420b9b4b46cab5519651caa/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebApkActivity.java
[modify] https://crrev.com/5c9311ed7789a0591420b9b4b46cab5519651caa/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappActivity.java
[modify] https://crrev.com/5c9311ed7789a0591420b9b4b46cab5519651caa/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappDataStorage.java
[modify] https://crrev.com/5c9311ed7789a0591420b9b4b46cab5519651caa/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappRegistry.java
[modify] https://crrev.com/5c9311ed7789a0591420b9b4b46cab5519651caa/chrome/android/javatests/src/org/chromium/chrome/browser/webapps/WebApkIntegrationTest.java
[modify] https://crrev.com/5c9311ed7789a0591420b9b4b46cab5519651caa/chrome/android/javatests/src/org/chromium/chrome/browser/webapps/WebappModeTest.java
[modify] https://crrev.com/5c9311ed7789a0591420b9b4b46cab5519651caa/chrome/android/junit/src/org/chromium/chrome/browser/webapps/WebappDataStorageTest.java
[modify] https://crrev.com/5c9311ed7789a0591420b9b4b46cab5519651caa/tools/metrics/histograms/histograms.xml