Fix a bunch of generated file build flakes in //extensions

extensions/browser/api/BUILD.gn

 # Copyright 2016 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("//build/json_schema_api.gni")
+import("//extensions/common/api/schema.gni")
+
 source_set("api") {
   sources = [
     "api_resource.cc",
     "api_resource.h",
     "api_resource_manager.h",
     "async_api_function.cc",
     "async_api_function.h",
     "device_permissions_manager.cc",
     "device_permissions_manager.h",
     "device_permissions_prompt.cc",
@@ skipping 53 matching lines @@
     "//extensions/browser/api/system_storage",
     "//extensions/browser/api/test",
     "//extensions/browser/api/usb",
     "//extensions/browser/api/virtual_keyboard_private",
     "//extensions/browser/api/web_request",
   ]
 
   deps = [
     "//base:i18n",
     "//content/public/browser",
+    "//extensions/strings",
   ]
 
   if (is_chromeos) {
     public_deps += [
       "//extensions/browser/api/diagnostics",
       "//extensions/browser/api/networking_config",
       "//extensions/browser/api/vpn_provider",
       "//extensions/browser/api/webcam_private",
     ]
   }
 }
+
+json_schema_api("api_registration") {
+  sources =
+      rebase_path(extensions_api_schema_files, ".", "//extensions/common/api")

[Devlin, 2016/10/27 16:00:59]

Can we assert() some of these as a sanity check?

[Dirk Pranke, 2016/10/27 21:28:44]

What would you be asserting?

+  impl_dir = "//extensions/browser/api"
+  bundle_registration = true
+  bundle_name = ""
+  root_namespace = extensions_api_root_namespace
+  uncompiled_sources = rebase_path(extensions_api_uncompiled_sources,
+                                   ".",
+                                   "//extensions/common/api")

[Devlin, 2016/10/27 16:00:59]

gn accepts fully qualified paths (e.g. //extensions/common/api/foo.json).  I
wonder if we could, in the schema.gni file, export the variables like that? 
Then we could just use them in their raw form here.

dpranke@, is that possible?  Something like an "source_path" function or the
like?  rebase_path(path, "//", "//extensions/common/api") wouldn't quite work
because it wouldn't produce the leading //.

(We could also hypothetically just do string addition -
"//extensions/common/api/" + path - but that seems a little more hacky.)

[Dirk Pranke, 2016/10/27 21:28:44]

Use get_path_info(extension_api_schema_files, "abspath"), etc., in schema.gni 
(see `gn help get_path_info` for more).

+
+  deps = [
+    ":api",
+    "//device/serial",
+    "//extensions/common/api",
+    "//extensions/common/api/cast_channel:cast_channel_proto",
+    "//skia",
+  ]
+}