Restructure public side of view_manager service.

mojo/services/view_manager/public/cpp/BUILD.gn

Index: mojo/services/view_manager/public/cpp/BUILD.gn
diff --git a/mojo/services/public/cpp/view_manager/BUILD.gn b/mojo/services/view_manager/public/cpp/BUILD.gn
similarity index 93%
rename from mojo/services/public/cpp/view_manager/BUILD.gn
rename to mojo/services/view_manager/public/cpp/BUILD.gn
index 14eb27d3fac0d17e2f5fa9083e3c572753db8aec..28f495b9cdd2b89a5b7c1309a99a4169fa122ea5 100644
--- a/mojo/services/public/cpp/view_manager/BUILD.gn
+++ b/mojo/services/view_manager/public/cpp/BUILD.gn
@@ -2,7 +2,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-source_set("view_manager") {
+source_set("cpp") {
   sources = [
     "lib/view.cc",
     "lib/view_manager_client_factory.cc",
@@ -35,7 +35,7 @@ source_set("view_manager") {
     "//mojo/services/public/interfaces/geometry",
     "//mojo/services/public/interfaces/input_events:input_events",
     "//mojo/services/public/interfaces/surfaces:surface_id",
-    "//mojo/services/public/interfaces/view_manager",
+    "//mojo/services/view_manager/public/interfaces",
     "//mojo/services/window_manager/public/interfaces",
   ]
 }