We could probably just capture a different measure - number of webapks installed via banner or menu (not # of launches per installation source). Then separately we can also track launches

https://docs.google.com/document/d/1pQPrHeI4L_jUZ8B8Sh4N0z_yiXwiFuoEhLl3AMXvt-I/edit#heading=h.1ctovw0c1tx (for install flow metrics)

Assigning this bug to Xi since she is already working on this (https://codereview.chromium.org/2301263004/)

We should also collect metrics for how often:
- we check whether the WebAPK should be updated
- request a WebAPK update

Dominick mentioned that those metrics would be useful in https://codereview.chromium.org/2331773002/

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2f4bcfddf49def3cf2f81700922f43390e06a8a5

commit 2f4bcfddf49def3cf2f81700922f43390e06a8a5
Author: hanxi <hanxi@chromium.org>
Date: Thu Sep 22 19:53:42 2016

Add WebAPK installation metrics.

Records metrics when WebAPK is installed via banner or add-to-homescreen menu,
including: install events, installation start types, and user actions.

Design doc: https://docs.google.com/document/d/1pQPrHeI4L_jUZ8B8Sh4N0z_yiXwiFuoEhLl3AMXvt-I/edit#heading=h.1ctovw0c1tx

BUG= 626510 

Review-Url: https://codereview.chromium.org/2301263004
Cr-Commit-Position: refs/heads/master@{#420433}

[modify] https://crrev.com/2f4bcfddf49def3cf2f81700922f43390e06a8a5/chrome/browser/BUILD.gn
[modify] https://crrev.com/2f4bcfddf49def3cf2f81700922f43390e06a8a5/chrome/browser/android/banners/app_banner_infobar_delegate_android.cc
[modify] https://crrev.com/2f4bcfddf49def3cf2f81700922f43390e06a8a5/chrome/browser/android/banners/app_banner_infobar_delegate_android.h
[add] https://crrev.com/2f4bcfddf49def3cf2f81700922f43390e06a8a5/chrome/browser/android/webapk/webapk_metrics.cc
[add] https://crrev.com/2f4bcfddf49def3cf2f81700922f43390e06a8a5/chrome/browser/android/webapk/webapk_metrics.h
[modify] https://crrev.com/2f4bcfddf49def3cf2f81700922f43390e06a8a5/tools/metrics/histograms/histograms.xml

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/07373421ccbda77a1a3882bd045fbf4ce1a707fa

commit 07373421ccbda77a1a3882bd045fbf4ce1a707fa
Author: hanxi <hanxi@chromium.org>
Date: Tue Sep 27 14:36:17 2016

Pass WebAPK install source to AppBannerInfobarDelegateAndroid constructor.

This is a follow up CL for CL (https://codereview.chromium.org/2301263004).
The InstallSource is passed into the constructor of
AppBannerInfoBarDelegationAndroid, so we can call Accept() instead of
AcceptWebApk() when installing a WebAPK from add-to-homescreen menu.

BUG= 626510 

Review-Url: https://codereview.chromium.org/2375503003
Cr-Commit-Position: refs/heads/master@{#421202}

[modify] https://crrev.com/07373421ccbda77a1a3882bd045fbf4ce1a707fa/chrome/browser/android/banners/app_banner_infobar_delegate_android.cc
[modify] https://crrev.com/07373421ccbda77a1a3882bd045fbf4ce1a707fa/chrome/browser/android/banners/app_banner_infobar_delegate_android.h
[modify] https://crrev.com/07373421ccbda77a1a3882bd045fbf4ce1a707fa/chrome/browser/android/banners/app_banner_manager_android.cc
[modify] https://crrev.com/07373421ccbda77a1a3882bd045fbf4ce1a707fa/chrome/browser/android/webapps/add_to_homescreen_manager.cc

Is this bug done?