Make content_shell_apk build completely

content/browser/BUILD.gn

 # 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.
 
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//content/browser/browser.gni")
+import("//media/media_options.gni")
 
 source_set("browser") {
   # Only the public target should depend on this. All other targets (even
   # internal content ones) should depend on the public one.
   visibility = [ "//content/public/browser:browser_sources" ]
 
   defines = []
   libs = []
   ldflags = []
 
@@ skipping 383 matching lines @@
   if (enable_web_speech) {
     deps += [
       "//third_party/flac",
       "//third_party/speex",
     ]
   }
 
   if (is_linux && use_dbus) {
       deps += [ "//dbus" ]
   }
+
+  if (enable_browser_cdms) {
+    sources += [
+      "media/cdm/browser_cdm_manager.cc",
+      "media/cdm/browser_cdm_manager.h",
+      "media/media_web_contents_observer.cc",
+      "media/media_web_contents_observer.h",
+    ]
+  }
 }