Decompose //extensions/browser/BUILD.gn

extensions/browser/api/messaging/BUILD.gn

Index: extensions/browser/api/messaging/BUILD.gn
diff --git a/tools/android/purge_ashmem/BUILD.gn b/extensions/browser/api/messaging/BUILD.gn
similarity index 66%
copy from tools/android/purge_ashmem/BUILD.gn
copy to extensions/browser/api/messaging/BUILD.gn
index e717fb137f6622d9b16db13a4f5b97eb81a7b49a..aa993fc614448f6c8ab886b4d96c5e2aecab89a5 100644
--- a/tools/android/purge_ashmem/BUILD.gn
+++ b/extensions/browser/api/messaging/BUILD.gn
@@ -1,12 +1,13 @@
 # Copyright 2015 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.
-
-executable("purge_ashmem") {
+source_set("messaging") {
   sources = [
-    "purge_ashmem.c",
+    "native_message_host.cc",
   ]
+
   deps = [
-    "//third_party/ashmem",
+    "//content/public/browser",
+    "//skia",
   ]
 }