chromeos: Add Screenshot_Annotate metric.

chrome/browser/ui/ash/chrome_screenshot_grabber.cc

Index: chrome/browser/ui/ash/chrome_screenshot_grabber.cc
diff --git a/chrome/browser/ui/ash/chrome_screenshot_grabber.cc b/chrome/browser/ui/ash/chrome_screenshot_grabber.cc
index 5d622d7cb937f18b0ea5576504d6a93743ad651d..77c973948c798ef6ad8d445075f86bd31f7c36a6 100644
--- a/chrome/browser/ui/ash/chrome_screenshot_grabber.cc
+++ b/chrome/browser/ui/ash/chrome_screenshot_grabber.cc
@@ -136,8 +136,10 @@ class ScreenshotGrabberNotificationDelegate : public NotificationDelegate {
         break;
       }
       case BUTTON_ANNOTATE: {
-        if (chromeos::IsNoteTakingAppAvailable(profile_))
+        if (chromeos::IsNoteTakingAppAvailable(profile_)) {
           chromeos::LaunchNoteTakingAppForNewNote(profile_, screenshot_path_);
+          content::RecordAction(base::UserMetricsAction("Screenshot_Annotate"));
+        }
         break;
       }
       default: