Add UseCounters for BeforeInstallPromptEvent.

Add UseCounters for BeforeInstallPromptEvent.

These stats will help identify how often developers catch the event and
call its methods.

BUG=625716
Committed: https://crrev.com/cad44b02ae8dd0acfbcbcd08fb5cce2a5e845f48
Cr-Commit-Position: refs/heads/master@{#404430}

[dominickn, 2016-07-05 07:54:55]

dominickn@chromium.org changed reviewers:
+ isherman@chromium.org, mlamouri@chromium.org

[dominickn, 2016-07-05 07:54:56]

PTAL, thanks! I haven't implemented one of these UseCounters before so I hope
this is doing it correctly. :)

[Ilya Sherman, 2016-07-06 23:03:40]

histograms.xml lgtm

[mlamouri (slow - plz ping), 2016-07-07 10:20:30]

lgtm

[dstockwell, 2016-07-08 01:42:27]

dstockwell@chromium.org changed reviewers:
+ dstockwell@chromium.org

[dstockwell, 2016-07-08 01:42:28]

lgtm

[dominickn, 2016-07-08 01:45:26]

The CQ bit was checked by dominickn@chromium.org

[dominickn, 2016-07-08 01:45:27]

The patchset sent to the CQ was uploaded after l-g-t-m from
isherman@chromium.org, mlamouri@chromium.org
Link to the patchset: https://codereview.chromium.org/2121083002/#ps20001
(title: "Rebase")

[commit-bot: I haz the power, 2016-07-08 01:45:43]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-07-08 14:27:26]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-07-08 14:27:29]

Failed to apply patch for third_party/WebKit/Source/core/frame/UseCounter.h:
While running git apply --index -3 -p1;
  error: patch failed: third_party/WebKit/Source/core/frame/UseCounter.h:1238
  Falling back to three-way merge...
  Applied patch to 'third_party/WebKit/Source/core/frame/UseCounter.h' with
conflicts.
  U third_party/WebKit/Source/core/frame/UseCounter.h

Patch:       third_party/WebKit/Source/core/frame/UseCounter.h
Index: third_party/WebKit/Source/core/frame/UseCounter.h
diff --git a/third_party/WebKit/Source/core/frame/UseCounter.h
b/third_party/WebKit/Source/core/frame/UseCounter.h
index
d86e35582b006553b1e05b8f6ad599809c6a7f92..e3d87899eed82dd62d90f4e7e3bee959970e378c
100644
--- a/third_party/WebKit/Source/core/frame/UseCounter.h
+++ b/third_party/WebKit/Source/core/frame/UseCounter.h
@@ -1238,6 +1238,10 @@ public:
         PointerEventDispatch = 1432,
         MIDIMessageEventReceivedTime = 1433,
         SummaryElementWithDisplayBlockAuthorRule = 1434,
+        BeforeInstallPromptEvent = 1435,
+        BeforeInstallPromptEventUserChoice = 1436,
+        BeforeInstallPromptEventPreventDefault = 1437,
+        BeforeInstallPromptEventPrompt = 1438,
 
         // Add new features immediately above this line. Don't change assigned
         // numbers of any item, and don't reuse removed slots.

[commit-bot: I haz the power, 2016-07-08 14:27:49]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-07-08 14:27:50]

CQ bit was unchecked.

[dominickn, 2016-07-08 14:39:53]

The CQ bit was checked by dominickn@chromium.org

[dominickn, 2016-07-08 14:39:54]

The patchset sent to the CQ was uploaded after l-g-t-m from
dstockwell@chromium.org, isherman@chromium.org, mlamouri@chromium.org
Link to the patchset: https://codereview.chromium.org/2121083002/#ps40001
(title: "Rebase")

[commit-bot: I haz the power, 2016-07-08 14:40:17]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-07-08 17:39:04]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2016-07-08 17:39:21]

CQ bit was unchecked.

[commit-bot: I haz the power, 2016-07-08 17:41:30]

Description was changed from

==========
Add UseCounters for BeforeInstallPromptEvent.

These stats will help identify how often developers catch the event and
call its methods.

BUG=625716
==========

to

==========
Add UseCounters for BeforeInstallPromptEvent.

These stats will help identify how often developers catch the event and
call its methods.

BUG=625716

Committed: https://crrev.com/cad44b02ae8dd0acfbcbcd08fb5cce2a5e845f48
Cr-Commit-Position: refs/heads/master@{#404430}
==========

[commit-bot: I haz the power, 2016-07-08 17:41:32]

Patchset 3 (id:??) landed as
https://crrev.com/cad44b02ae8dd0acfbcbcd08fb5cce2a5e845f48
Cr-Commit-Position: refs/heads/master@{#404430}