Move json schema compiler target into build/ to match gyp

ui/accessibility/BUILD.gn

Index: ui/accessibility/BUILD.gn
diff --git a/ui/accessibility/BUILD.gn b/ui/accessibility/BUILD.gn
index 9300120a2a06e40afd0391194111136cfd84706f..fbe8b66104a9caa24a5a5fa5fda88fb349729be4 100644
--- a/ui/accessibility/BUILD.gn
+++ b/ui/accessibility/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.
 
-import("//extensions/generated_extensions_api.gni")
+import("//build/json_schema_compile.gni")
 
 component("accessibility") {
   sources = [
@@ -71,7 +71,7 @@ test("accessibility_unittests") {
   ]
 }
 
-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"