[Android] Add UMA for pull-to-refresh activation

Add a baseline metric for the number of page reloads triggered by the
new pull-to-refresh gesture, allowing comparison with other avenues
for page reload (e.g., from toolbar reload icon).

BUG=442505

Review URL: https://codereview.chromium.org/803343002

Cr-Commit-Position: refs/heads/master@{#308477}

content/browser/android/overscroll_controller_android.cc

@@ -13,6 +13,7 @@
 #include "content/browser/web_contents/web_contents_impl.h"
 #include "content/common/input/did_overscroll_params.h"
 #include "content/public/browser/navigation_controller.h"
+#include "content/public/browser/user_metrics.h"
 #include "content/public/common/content_switches.h"
 #include "third_party/WebKit/public/web/WebInputEvent.h"
 #include "ui/android/resources/resource_manager.h"
@@ -277,6 +278,7 @@ void OverscrollControllerAndroid::TriggerRefresh() {
     return;
 
   triggered_refresh_active_ = true;
+  RecordAction(base::UserMetricsAction("MobilePullGestureReload"));
   web_contents()->GetController().Reload(true);
 }
 

tools/metrics/actions/actions.xml

@@ -7575,6 +7575,15 @@ should be able to be added at any place in this file.
   <description>User closes the tab while preview page is loaded.</description>
 </action>
 
+<action name="MobilePullGestureReload">
+  <owner>jdduke@chromium.org</owner>
+  <description>
+    Emitted on Android when a pull-to-refresh touch gesture initiates a page
+    reload. This fires only after the triggering touch is released while the
+    refresh effect has been pulled beyond the activation threshold.
+  </description>
+</action>
+
 <action name="MobileReceivedExternalIntent">
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <description>Please enter the description of this user action.</description>

tools/metrics/actions/extract_actions.py

@@ -287,6 +287,7 @@ def AddAndroidActions(actions):
   actions.add('MobilePageLoaded')
   actions.add('MobilePageLoadedDesktopUserAgent')
   actions.add('MobilePageLoadedWithKeyboard')
+  actions.add('MobilePullGestureReload')
   actions.add('MobileReceivedExternalIntent')
   actions.add('MobileRendererCrashed')
   actions.add('MobileShortcutAllBookmarks')