Add the ability to configure feedback prompt frequency

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 aa7a4510154561effb0054a97da7f28327318d3e..8b68eb3f1b29fd802f818a311631b00a95b5fced 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
@@ -89,9 +89,6 @@ public class VrShellDelegate implements ApplicationStatus.ActivityStateListener,
 
     private static final long REENTER_VR_TIMEOUT_MS = 1000;
 
-    // TODO(ymalik): This should be configurable via Finch.
-    private static final int FEEDBACK_FREQUENCY = 10;
-
     private static final int VR_SYSTEM_UI_FLAGS = View.SYSTEM_UI_FLAG_LAYOUT_STABLE
             | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
             | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION | View.SYSTEM_UI_FLAG_FULLSCREEN
@@ -336,7 +333,8 @@ public class VrShellDelegate implements ApplicationStatus.ActivityStateListener,
     }
 
     private static boolean activitySupportsExitFeedback(Activity activity) {
-        return activity instanceof ChromeTabbedActivity;
+        return activity instanceof ChromeTabbedActivity
+                && ChromeFeatureList.isEnabled(ChromeFeatureList.VR_BROWSING_FEEDBACK);
     }
 
     /**
@@ -413,7 +411,7 @@ public class VrShellDelegate implements ApplicationStatus.ActivityStateListener,
         mPaused = ApplicationStatus.getStateForActivity(activity) != ActivityState.RESUMED;
         updateVrSupportLevel();
         mNativeVrShellDelegate = nativeInit();
-        mFeedbackFrequency = FEEDBACK_FREQUENCY;
+        mFeedbackFrequency = VrFeedbackStatus.getFeedbackFrequency();

[amp, 2017/05/20 00:12:04]

Have you verified this works?  I think native libraries need to be loaded before
you can check a feature (or get params from them).

I'm not sure they will be ready when VrShellDelegate is being constructed.

But if it worked for you then it is probably fine.

[mthiesse, 2017/05/20 01:52:44]

VrShellDelegate can only be constructed after the native libraries are loaded
(you'll notice the nativeInit() call right above this one)

[ymalik, 2017/05/22 22:35:01]

+1,  native libraries should be loaded at this point.

         Choreographer choreographer = Choreographer.getInstance();
         choreographer.postFrameCallback(new FrameCallback() {
             @Override