Media Keys should not count towards the max of four shortcuts per extension.

chrome/common/extensions/command.h

Index: chrome/common/extensions/command.h
diff --git a/chrome/common/extensions/command.h b/chrome/common/extensions/command.h
index 0ea3fe4924cfc3a3a5637d29bfeb59008845a30e..41ec35aa503dae6a57d5139112a2759e6a845291 100644
--- a/chrome/common/extensions/command.h
+++ b/chrome/common/extensions/command.h
@@ -42,6 +42,11 @@ class Command {
   // shortcut text (like accelerator::GetShortcutText() does).
   static std::string AcceleratorToString(const ui::Accelerator& accelerator);
 
+  // Return true if the specified accelerator is one of the following multimedia
+  // keys: Next Track key, Previous Track key, Stop Media key, Play/Pause Media
+  // key, without any modifiers.
+  static bool IsMediaKey(const ui::Accelerator& accelerator);
+
   // Parse the command.
   bool Parse(const base::DictionaryValue* command,
              const std::string& command_name,