FBTF: Clean up task.h in x11_util.h and header usage in some delegates.

chrome/browser/modal_html_dialog_delegate.h

Index: chrome/browser/modal_html_dialog_delegate.h
diff --git a/chrome/browser/modal_html_dialog_delegate.h b/chrome/browser/modal_html_dialog_delegate.h
index bbc21b6d429669ee67e64485ff5d4e86e9c91bc0..e734756f463a75f3eba9db0f366367b901217662 100644
--- a/chrome/browser/modal_html_dialog_delegate.h
+++ b/chrome/browser/modal_html_dialog_delegate.h
@@ -10,8 +10,14 @@
 
 #include "chrome/browser/dom_ui/html_dialog_ui.h"
 #include "chrome/common/notification_registrar.h"
-#include "gfx/size.h"
-#include "ipc/ipc_message.h"
+
+namespace gfx {
+class Size;
+}
+
+namespace IPC {
+class Message;
+}
 
 // This class can only be used on the UI thread.
 class ModalHtmlDialogDelegate