Add a simple browser UI (with url bar)

mandoline/ui/aura/surface_context_factory.cc

Index: mandoline/ui/aura/surface_context_factory.cc
diff --git a/mandoline/ui/aura/surface_context_factory.cc b/mandoline/ui/aura/surface_context_factory.cc
index 0c5af87b90514a6a590e30eb0fc0cfddfc3d729a..1253675d60635e9379fad0cff4ff146e814a8926 100644
--- a/mandoline/ui/aura/surface_context_factory.cc
+++ b/mandoline/ui/aura/surface_context_factory.cc
@@ -28,7 +28,8 @@ class FakeReflector : public ui::Reflector {
 
 SurfaceContextFactory::SurfaceContextFactory(mojo::Shell* shell,
                                              mojo::View* view)
-    : surface_binding_(shell, view) {
+    : surface_binding_(shell, view),
+      next_surface_id_namespace_(1u) {
 }
 
 SurfaceContextFactory::~SurfaceContextFactory() {
@@ -88,8 +89,8 @@ cc::TaskGraphRunner* SurfaceContextFactory::GetTaskGraphRunner() {
 
 scoped_ptr<cc::SurfaceIdAllocator>
 SurfaceContextFactory::CreateSurfaceIdAllocator() {
-  NOTIMPLEMENTED();
-  return nullptr;
+  return make_scoped_ptr(
+      new cc::SurfaceIdAllocator(next_surface_id_namespace_++));
 }
 
 void SurfaceContextFactory::ResizeDisplay(ui::Compositor* compositor,