Refactor extension handling code from AppShimHost into ExtensionAppShimHandler.

apps/app_shim/app_shim_handler_mac.h

Index: apps/app_shim/app_shim_handler_mac.h
diff --git a/apps/app_shim/app_shim_handler_mac.h b/apps/app_shim/app_shim_handler_mac.h
index 6a694c0a0a3107e88e106229af8cc7bf3d4be880..c0fc87ac47d438e112bddde320688d6084a52d28 100644
--- a/apps/app_shim/app_shim_handler_mac.h
+++ b/apps/app_shim/app_shim_handler_mac.h
@@ -7,6 +7,8 @@
 
 #include <string>
 
+class Profile;
+
 namespace apps {
 
 // Registrar, and interface for services that can handle interactions with OSX
@@ -18,6 +20,10 @@ class AppShimHandler {
     // Invoked when the app is closed in the browser process.
     virtual void OnAppClosed() = 0;
 
+    // Allows the handler to determine which app this host corresponds to.
+    virtual Profile* profile() const = 0;

[tapted, 2013/05/21 06:15:37]

Since there is no corresponding data member at this level, I think these need to
be TitleCase -- Profile, AppId -- rather than hacker_style. (Then, I'd just
rename the functions lower down rather than having accessors as well).

[jackhou1, 2013/05/22 23:54:44]

Done.

+    virtual const std::string& app_id() const = 0;

[tapted, 2013/05/21 06:15:37]

nit: Maybe drop the reference and just return std::string (avoids imposing an
implementation detail on concrete types, but it's a bit academic here).

[jackhou1, 2013/05/22 23:54:44]

Done.

+
    protected:
     virtual ~Host() {}
   };
@@ -29,10 +35,14 @@ class AppShimHandler {
   // Remove a handler for an |app_mode_id|.
   static void RemoveHandler(const std::string& app_mode_id);
 
-  // Returns the handler registered for the given |app_mode_id|, or NULL if none
-  // is registered.
+  // Returns the handler registered for the given |app_mode_id|, or the default
+  // handler if none is registered, or NULL if there is no default handler.

[tapted, 2013/05/21 06:15:37]

nit: comment reads a bit funny. Maybe just drop the first "or"

[jackhou1, 2013/05/22 23:54:44]

Done.

   static AppShimHandler* GetForAppMode(const std::string& app_mode_id);
 
+  // Sets the default handler to return when there is no app-specific handler.
+  // Setting this to NULL removes the default handler.
+  static void SetDefaultHandler(AppShimHandler* handler);
+
   // Invoked by the shim host when the shim process is launched. The handler
   // must return true if successful, or false to indicate back to the shim
   // process that it should close.