Pause/resume other windows when entering/exiting immersive mode

app/src/common/shared/org/mozilla/vrbrowser/VRBrowserActivity.java

@@ -799,6 +799,7 @@ void pauseGeckoViewCompositor() {
             return;
         }
         mIsPresentingImmersive = true;
+        mWindows.enterImmersiveMode();
         TelemetryWrapper.startImmersive();
         PauseCompositorRunnable runnable = new PauseCompositorRunnable();
 
@@ -821,6 +822,7 @@ void resumeGeckoViewCompositor() {
             return;
         }
         mIsPresentingImmersive = false;
+        mWindows.exitImmersiveMode();
         // Show the window in front of you when you exit immersive mode.
         resetUIYaw();
 

app/src/common/shared/org/mozilla/vrbrowser/ui/widgets/Windows.java

@@ -395,6 +395,31 @@ public boolean isInPrivateMode() {
         return mPrivateMode;
     }
 
+    public void enterImmersiveMode() {
+        for (WindowWidget window: mRegularWindows) {
+            if (window != mFocusedWindow) {
+                window.onPause();
+            }
+        }
+        for (WindowWidget window: mPrivateWindows) {
+            if (window != mFocusedWindow) {
+                window.onPause();
+            }
+        }
+    }
+
+    public void exitImmersiveMode() {
+        for (WindowWidget window: mRegularWindows) {
+            if (window != mFocusedWindow) {
+                window.onResume();
+            }
+        }
+        for (WindowWidget window: mPrivateWindows) {
+            if (window != mFocusedWindow) {
+                window.onResume();
+            }
+        }
+    }
 
     public void enterPrivateMode() {
         if (mPrivateMode) {