Add UMA metrics to track user action sequence in VR

chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java

Index: chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java b/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java
index 6ea8491b9e3b41178fd4b9e600c6f154c81474e1..82a5e186e60305a237912c97e74d1b963295498b 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java
@@ -37,6 +37,7 @@ import org.chromium.base.VisibleForTesting;
 import org.chromium.base.annotations.CalledByNative;
 import org.chromium.base.annotations.JNINamespace;
 import org.chromium.base.library_loader.LibraryLoader;
+import org.chromium.base.metrics.RecordUserAction;
 import org.chromium.chrome.R;
 import org.chromium.chrome.browser.ChromeActivity;
 import org.chromium.chrome.browser.ChromeFeatureList;
@@ -470,6 +471,9 @@ public class VrShellDelegate implements ApplicationStatus.ActivityStateListener,
         // in the vrdisplayactivate handler we will exit presentation later.
         enterVr(mListeningForWebVrActivateBeforePause && !mRequestedWebVr);
 
+        // The user has successfully completed a DON flow.
+        RecordUserAction.record("VR.DON");
+
         return true;
     }
 
@@ -755,6 +759,10 @@ public class VrShellDelegate implements ApplicationStatus.ActivityStateListener,
             mVrClassesWrapper.setVrModeEnabled(mActivity, false);
             mLastVrExit = SystemClock.uptimeMillis();
         }
+
+        // The user has exited VR.
+        RecordUserAction.record("VR.DOFF");
+
         restoreWindowMode();
         mVrShell.pause();
         removeVrViews();