Implemented event-dispatching for button clicks.

chrome/browser/ui/webui/chromeos/login/base_screen_handler.cc

Index: chrome/browser/ui/webui/chromeos/login/base_screen_handler.cc
diff --git a/chrome/browser/ui/webui/chromeos/login/base_screen_handler.cc b/chrome/browser/ui/webui/chromeos/login/base_screen_handler.cc
index a421236bf5104b837cf91ef4db2e75bcccc758b5..cb40f723cd9261a9660846d539acb0ba138be518 100644
--- a/chrome/browser/ui/webui/chromeos/login/base_screen_handler.cc
+++ b/chrome/browser/ui/webui/chromeos/login/base_screen_handler.cc
@@ -86,6 +86,8 @@ void BaseScreenHandler::GetLocalizedStrings(base::DictionaryValue* dict) {
 }
 
 void BaseScreenHandler::RegisterMessages() {
+  AddPrefixedCallback("buttonClicked",
+                      &BaseScreenHandler::HandleButtonClicked);
   AddPrefixedCallback("contextChanged",
                       &BaseScreenHandler::HandleContextChanged);
   DeclareJSCallbacks();
@@ -118,6 +120,11 @@ std::string BaseScreenHandler::FullMethodPath(const std::string& method) const {
   return js_screen_path_prefix_ + method;
 }
 
+void BaseScreenHandler::HandleButtonClicked(const std::string& button_id) {
+  if (base_screen_)
+    base_screen_->OnButtonClicked(button_id);
+}
+
 void BaseScreenHandler::HandleContextChanged(
     const base::DictionaryValue* diff) {
   if (diff && base_screen_)