Decompose //extensions/browser/BUILD.gn

extensions/browser/api/alarms/BUILD.gn

Index: extensions/browser/api/alarms/BUILD.gn
diff --git a/extensions/browser/api/alarms/BUILD.gn b/extensions/browser/api/alarms/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..168274f2559de195d0576bf5d2e87d1ad3670a35
--- /dev/null
+++ b/extensions/browser/api/alarms/BUILD.gn
@@ -0,0 +1,18 @@
+# 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.
+
+source_set("alarms") {
+  sources = [
+    "alarm_manager.cc",
+    "alarm_manager.h",
+    "alarms_api.cc",
+    "alarms_api.h",
+    "alarms_api_constants.cc",
+    "alarms_api_constants.h",
+  ]
+
+  deps = [
+    "//extensions/common/api",
+  ]
+}