Move json schema compiler target into build/ to match gyp

ui/accessibility/BUILD.gn

 # Copyright 2014 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("//extensions/generated_extensions_api.gni")
+import("//build/json_schema_compile.gni")
 
 component("accessibility") {
   sources = [
     "ax_node.cc",
     "ax_node.h",
     "ax_node_data.cc",
     "ax_node_data.h",
     "ax_serializable_tree.cc",
     "ax_serializable_tree.h",
     "ax_text_utils.cc",
@@ skipping 48 matching lines @@
     ":accessibility",
     ":test_support",
     "//base",
     "//base/test:run_all_unittests",
     "//testing/gtest",
     "//ui/gfx",
     "//ui/gfx/geometry",
   ]
 }
 
-generated_extensions_api("ax_gen") {
+json_schema_compile("ax_gen") {

[brettw, 2014/09/23 21:42:57]

I wonder if we should pick a different name. I recall that the GYP one has
separate steps for compile and bundle, while the GN template does both. maybe
"json_schema_api"?

   sources = [ "ax_enums.idl" ]
   deps = [ "//base/third_party/dynamic_annotations" ]
   root_namespace = "ui"
   schemas = true
 }