Android: Don't destroy LayerTreeHost when Surface goes away

ui/android/resources/ui_resource_android.cc

Index: ui/android/resources/ui_resource_android.cc
diff --git a/ui/android/resources/ui_resource_android.cc b/ui/android/resources/ui_resource_android.cc
index bc85bb88666a50033e24bc5d439c364d9ce7d5ab..89ed2ed922cf4015ae9981bdb84b4850401550c7 100644
--- a/ui/android/resources/ui_resource_android.cc
+++ b/ui/android/resources/ui_resource_android.cc
@@ -38,10 +38,6 @@ cc::UIResourceId UIResourceAndroid::id() {
   return id_;
 }
 
-void UIResourceAndroid::UIResourceIsInvalid() {
-  id_ = 0;
-}
-
 UIResourceAndroid::UIResourceAndroid(ui::UIResourceProvider* provider,
                                      const SkBitmap& skbitmap)
     : provider_(provider), bitmap_(skbitmap), id_(0) {