webui: rename "DialogClose" to "dialogClose" to match other webui messages.

ui/web_dialogs/web_dialog_ui.cc

Index: ui/web_dialogs/web_dialog_ui.cc
diff --git a/ui/web_dialogs/web_dialog_ui.cc b/ui/web_dialogs/web_dialog_ui.cc
index c0ffb02b8e4d30b27bfe8fca8d3b41687f7ec2c4..161af45c0449b2f725c8a7cb82c0bb43c94a1217 100644
--- a/ui/web_dialogs/web_dialog_ui.cc
+++ b/ui/web_dialogs/web_dialog_ui.cc
@@ -79,7 +79,7 @@ WebDialogDelegate* WebDialogUI::GetDelegate(
 void WebDialogUI::RenderViewCreated(RenderViewHost* render_view_host) {
   // Hook up the javascript function calls, also known as chrome.send("foo")
   // calls in the HTML, to the actual C++ functions.
-  web_ui()->RegisterMessageCallback("DialogClose",
+  web_ui()->RegisterMessageCallback("dialogClose",
       base::Bind(&WebDialogUI::OnDialogClosed, base::Unretained(this)));
 
   // Pass the arguments to the renderer supplied by the delegate.