services/ui: Create a proper component for the client-lib.

services/ui/public/cpp/BUILD.gn

Index: services/ui/public/cpp/BUILD.gn
diff --git a/services/ui/public/cpp/BUILD.gn b/services/ui/public/cpp/BUILD.gn
index 001833b4fc759c60157e044507d3ae5d3242f353..3cbbdef1b6e8d39eb06cfc8558e41202ac408d1b 100644
--- a/services/ui/public/cpp/BUILD.gn
+++ b/services/ui/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("cpp") {
+component("cpp") {
   sources = [
     "bitmap_uploader.h",
     "context_provider.h",
@@ -31,6 +31,7 @@ source_set("cpp") {
     "property_type_converters.h",
     "raster_thread_helper.h",
     "scoped_window_ptr.h",
+    "ui_export.h",
     "window.h",
     "window_manager_delegate.cc",
     "window_manager_delegate.h",
@@ -75,5 +76,8 @@ source_set("cpp") {
     "//services/ui",
   ]
 
-  defines = [ "GL_GLEXT_PROTOTYPES" ]
+  defines = [
+    "GL_GLEXT_PROTOTYPES",
+    "UI_IMPLEMENTATION",
+  ]
 }