Polish the keybinding implementation a bit.

chrome/common/extensions/extension.h

Index: chrome/common/extensions/extension.h
===================================================================
--- chrome/common/extensions/extension.h	(revision 127690)
+++ chrome/common/extensions/extension.h	(working copy)
@@ -151,6 +151,12 @@
 
   class ExtensionKeybinding {
    public:
+    enum Type {
+      BROWSER_ACTION,
+      PAGE_ACTION,
+      COMMANDS,
+    };
+
     // Define out of line constructor/destructor to please Clang.
     ExtensionKeybinding();
     ~ExtensionKeybinding();
@@ -523,6 +529,11 @@
   // Returns true if the extension should be displayed in the launcher.
   bool ShouldDisplayInLauncher() const;
 
+  // Gets an extension keybindings by |type|.
+  void GetCommandByType(
+      Extension::ExtensionKeybinding::Type type,
+      std::vector<Extension::ExtensionKeybinding>* keybindings) const;
+
   // Accessors:
 
   const FilePath& path() const { return path_; }
@@ -551,6 +562,8 @@
   const std::vector<InputComponentInfo>& input_components() const {
     return input_components_;
   }
+  // See also GetCommandByType, which allows finer grained control over
+  // which commands are returned.
   const std::vector<ExtensionKeybinding>& keybindings() const {
     return commands_;
   }