Make content_shell_apk build completely

content/browser/BUILD.gn

Index: content/browser/BUILD.gn
diff --git a/content/browser/BUILD.gn b/content/browser/BUILD.gn
index f4d4d7ade65181b190889adbf3a1bfeae53630d3..5a565bb2291c2da21ee5693b0d645f538cd57d04 100644
--- a/content/browser/BUILD.gn
+++ b/content/browser/BUILD.gn
@@ -5,6 +5,7 @@
 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
@@ -413,4 +414,13 @@ source_set("browser") {
   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",
+    ]
+  }
 }