Split bundle generation steps so that API registration is generated in browser, not common.

extensions/common/api/schemas.gni

Index: extensions/common/api/schemas.gni
diff --git a/extensions/common/api/schemas.gni b/extensions/common/api/schemas.gni
new file mode 100644
index 0000000000000000000000000000000000000000..cf08efb4eaa67f5af32724ea8f222786e27ca2b6
--- /dev/null
+++ b/extensions/common/api/schemas.gni
@@ -0,0 +1,21 @@
+# 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.
+
+gypi_values = exec_script(
+    "//build/gypi_to_gn.py",
+    [ rebase_path("schemas.gypi") ],
+    "scope",
+    [ "schemas.gypi" ])
+
+if (is_android) {
+  sources = gypi_values.android_schema_files
+} else {
+  sources = gypi_values.main_schema_files
+}
+
+root_namespace = "extensions::core_api::%(namespace)s"
+deps = [
+  "//device/serial",
+  "//skia",
+]