Add support for HTTP handlers that are in self-contained apps. Also add an example app.

examples/http_handler/BUILD.gn

Index: examples/http_handler/BUILD.gn
diff --git a/examples/wget/BUILD.gn b/examples/http_handler/BUILD.gn
similarity index 62%
copy from examples/wget/BUILD.gn
copy to examples/http_handler/BUILD.gn
index 2fbc086bdfb005f96beeb9c8451e282458497631..824edffb4b21396eaf68d99bfdcdc61922db0061 100644
--- a/examples/wget/BUILD.gn
+++ b/examples/http_handler/BUILD.gn
@@ -2,16 +2,16 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-shared_library("wget") {
+shared_library("http_handler") {
+  sources = [
+    "http_handler.cc"
+  ]
+
   deps = [
+    "//mojo/application",
     "//mojo/public/c/system:for_shared_library",
-    "//mojo/public/cpp/application:standalone",
     "//mojo/public/cpp/bindings",
-    "//mojo/public/cpp/utility",
-    "//mojo/services/public/interfaces/network",
-  ]
-
-  sources = [
-    "wget.cc"
+    "//services/http_server",
+    "//services/http_server/public",
   ]
 }