Break up chrome/common:common

chrome/common/media_galleries/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.
+
+source_set("media_galleries") {
+  sources = [
+    "metadata_types.h",
+  ]
+  if (is_win || is_mac) {
+    sources += [
+      "itunes_library.cc",
+      "itunes_library.h",
+      "picasa_types.cc",
+      "picasa_types.h",
+      "pmp_constants.h",
+    ]
+  }
+  if (is_android) {
+    sources -= [ "metadata_types.h" ]
+  }
+  deps = [
+    "//base",
+    "//ipc",
+  ]
+}