Add histogram for browser-verification status of user activation.

We are running a Finch trial and we would like to know how many times
the browser process fails to verify User Activation.

Bug: 1098466, 1098467
Change-Id: I28572dd8bf5eb600efa13732bd8f64a316f2d3ba
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2418974
Commit-Queue: Liviu Tinta <liviutinta@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: Mustaq Ahmed <mustaq@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#811441}

content/browser/renderer_host/frame_tree_node.cc

@@ -13,6 +13,7 @@
 #include "base/feature_list.h"
 #include "base/lazy_instance.h"
 #include "base/macros.h"
+#include "base/metrics/histogram_functions.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/stl_util.h"
 #include "base/strings/string_util.h"
@@ -656,8 +657,12 @@ bool FrameTreeNode::UpdateUserActivationState(
       update_result = NotifyUserActivation(notification_type);
       break;
     case blink::mojom::UserActivationUpdateType::
-        kNotifyActivationPendingBrowserVerification:
-      if (VerifyUserActivation()) {
+        kNotifyActivationPendingBrowserVerification: {
+      const bool user_activation_verified = VerifyUserActivation();
+      // Add UMA metric for when browser user activation verification succeeds
+      base::UmaHistogramBoolean("Event.BrowserVerifiedUserActivation",
+                                user_activation_verified);
+      if (user_activation_verified) {
         update_result = NotifyUserActivation(
             blink::mojom::UserActivationNotificationType::kNone);
         update_type = blink::mojom::UserActivationUpdateType::kNotifyActivation;
@@ -667,7 +672,7 @@ bool FrameTreeNode::UpdateUserActivationState(
         // unrelated tests that inject event to renderer fail.
         return false;
       }
-      break;
+    } break;
     case blink::mojom::UserActivationUpdateType::kClearActivation:
       update_result = ClearUserActivation();
       break;

tools/metrics/histograms/histograms_xml/event/histograms.xml

@@ -75,6 +75,18 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
   </summary>
 </histogram>
 
+<histogram name="Event.BrowserVerifiedUserActivation" enum="BooleanSuccess"
+    expires_after="2020-12-31">
+  <owner>liviutinta@chromium.org</owner>
+  <owner>mustaq@chromium.org</owner>
+  <owner>input-dev@chromium.org</owner>
+  <summary>
+    Records whether Browser User Activation Verification is successful or not.
+    We are interested in how many times the Browser User Activation Verification
+    fails vs how many times it succeeds.
+  </summary>
+</histogram>
+
 <histogram name="Event.ClickNotFiredDueToDomManipulation" enum="BooleanHit"
     expires_after="M82">
   <owner>nzolghadr@chromium.org</owner>