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

ppapi/examples/2d/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("2d") {
+  testonly = true
+  deps = [
+    ":graphics_2d",
+    ":paint_manager",
+    ":scroll",
+  ]
+}
+
+ppapi_example("graphics_2d") {
+  output_name = "ppapi_example_graphics_2d"
+  sources = [
+    "graphics_2d_example.c",
+  ]
+  deps = [
+    "//ppapi/c",
+  ]
+}
+
+ppapi_example("paint_manager") {
+  output_name = "ppapi_example_paint_manager"
+  sources = [
+    "paint_manager_example.cc",
+  ]
+  deps = [
+    "//ppapi/cpp",
+  ]
+}
+
+ppapi_example("scroll") {
+  output_name = "ppapi_example_scroll"
+  sources = [
+    "scroll.cc",
+  ]
+  deps = [
+    "//ppapi/cpp",
+  ]
+}