Record when the Cast dialog is opened via the app menu

Record in the MediaRouter.Icon.Click.Location histogram whenever the
Cast dialog is opened via the "Cast..." item in the three-dots app menu.

Bug: 870032
Change-Id: I11fe3addaab40c1299bdc08dd0991fb3cb58f3c8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1906769
Commit-Queue: Takumi Fujimoto <takumif@chromium.org>
Reviewed-by: Peter Boström <pbos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#714578}

chrome/browser/media/router/media_router_metrics.h

@@ -22,7 +22,7 @@ enum class SinkIconType;
 
 // NOTE: Do not renumber enums as that would confuse interpretation of
 // previously logged data. When making changes, also update the enum list
-// in tools/metrics/histograms/histograms.xml to keep it in sync.
+// in tools/metrics/histograms/enums.xml to keep it in sync.
 
 // NOTE: For metrics specific to the Media Router component extension, see
 // mojo/media_router_mojo_metrics.h.
@@ -33,9 +33,10 @@ enum class MediaRouterDialogOpenOrigin {
   OVERFLOW_MENU = 1,
   CONTEXTUAL_MENU = 2,
   PAGE = 3,
+  APP_MENU = 4,
 
   // NOTE: Add entries only immediately above this line.
-  TOTAL_COUNT = 4
+  TOTAL_COUNT = 5
 };
 
 // The possible outcomes from a route creation response.

chrome/browser/ui/toolbar/app_menu_model.cc

@@ -24,6 +24,7 @@
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/defaults.h"
 #include "chrome/browser/media/router/media_router_feature.h"
+#include "chrome/browser/media/router/media_router_metrics.h"
 #include "chrome/browser/prefs/incognito_mode_prefs.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/profiles/profile_manager.h"
@@ -443,6 +444,10 @@ void AppMenuModel::LogMenuMetrics(int command_id) {
       if (!uma_action_recorded_)
         UMA_HISTOGRAM_MEDIUM_TIMES("WrenchMenu.TimeToAction.Cast", delta);
       LogMenuAction(MENU_ACTION_CAST);
+      // TODO(takumif): Look into moving this metrics logging to a single
+      // location, like MediaRouterDialogController::ShowMediaRouterDialog().
+      media_router::MediaRouterMetrics::RecordMediaRouterDialogOrigin(
+          media_router::MediaRouterDialogOpenOrigin::APP_MENU);
       break;
 
     // Edit menu.

tools/metrics/histograms/enums.xml

@@ -40883,6 +40883,7 @@ Called by update_use_counter_css.py.-->
   <int value="1" label="Overflow Menu"/>
   <int value="2" label="Contextual Menu"/>
   <int value="3" label="Page"/>
+  <int value="4" label="App Menu"/>
 </enum>
 
 <enum name="MediaRouterDialParseMessageResult">