Implement the rest of the PPAPI examples in the GN build.

ppapi/examples/url_loader/BUILD.gn

+# Copyright 2015 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import("//ppapi/examples/ppapi_example.gni")
+
+group("url_loader") {
+  testonly = true
+  deps = [
+    ":file",
+    ":streaming",
+  ]
+}
+
+ppapi_example("file") {
+  output_name = "ppapi_example_url_loader"
+  sources = [
+    "streaming.cc",
+  ]
+  deps = [
+    "//ppapi/cpp",
+  ]
+}
+
+ppapi_example("streaming") {
+  output_name = "ppapi_example_file"
+  sources = [
+    "stream_to_file.cc",
+  ]
+  deps = [
+    "//ppapi/cpp",
+  ]
+}