Eliminate all UI thread decoding of extension images....

chrome/browser/cocoa/extensions/extension_action_context_menu.mm

Index: chrome/browser/cocoa/extensions/extension_action_context_menu.mm
===================================================================
--- chrome/browser/cocoa/extensions/extension_action_context_menu.mm	(revision 42429)
+++ chrome/browser/cocoa/extensions/extension_action_context_menu.mm	(working copy)
@@ -73,8 +73,8 @@
     if (!browser)
       return;
 
-    ExtensionInstallUI client(browser->profile());
-    client.ConfirmUninstall(this, extension_, uninstall_icon->get());
+    install_ui_.reset(new ExtensionInstallUI(browser->profile()));
+    install_ui_->ConfirmUninstall(this, extension_);
   }
 
   // The extension that we're loading the icon for. Weak.
@@ -83,6 +83,8 @@
   // The uninstall icon shown by the confirmation dialog.
   scoped_ptr<SkBitmap> uninstall_icon_;
 
+  scoped_ptr<ExtensionInstallUI> install_ui_;
+
   DISALLOW_COPY_AND_ASSIGN(AsyncUninstaller);
 };