Don't drop all children when changing Android root layer.

content/browser/renderer_host/compositor_impl_android.cc

Index: content/browser/renderer_host/compositor_impl_android.cc
diff --git a/content/browser/renderer_host/compositor_impl_android.cc b/content/browser/renderer_host/compositor_impl_android.cc
index 6232bcdb434467966c7e2ba5b0d99ad07063a930..47f037d17f4652d3c7e48c3539d9e1fdb4fc7bff 100644
--- a/content/browser/renderer_host/compositor_impl_android.cc
+++ b/content/browser/renderer_host/compositor_impl_android.cc
@@ -341,9 +341,14 @@ UIResourceProvider& CompositorImpl::GetUIResourceProvider() {
 }
 
 void CompositorImpl::SetRootLayer(scoped_refptr<cc::Layer> root_layer) {
-  root_layer_->RemoveAllChildren();
-  if (root_layer)
+  if (subroot_layer_) {
+    subroot_layer_->RemoveFromParent();
+    subroot_layer_ = NULL;
+  }
+  if (root_layer) {
+    subroot_layer_ = root_layer;
     root_layer_->AddChild(root_layer);
+  }
 }
 
 void CompositorImpl::SetWindowSurface(ANativeWindow* window) {