Adding an explicit listener for the VR mode close button

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

Index: chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShell.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShell.java b/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShell.java
index ceeb17eaf2d43b5521c3052008390acc0aeff376..0ba4f3617bb3e2eeb361560e85de553c4fe1014b 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShell.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShell.java
@@ -47,4 +47,9 @@ public interface VrShell {
      * Returns the GVRLayout as a FrameLayout.
      */
     FrameLayout getContainer();
+
+    /**
+     * Sets a callback to be run when the close button is tapped.
+     */
+    void setCloseButtonListener(Runnable runner);
 }