Added 'contextReady' message for HostPairingScreen.

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

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/webui/chromeos/login/host_pairing_screen_handler.h"
 
 #include "chrome/browser/ui/webui/chromeos/login/oobe_ui.h"
 
 namespace chromeos {
 
 namespace {
 
 const char kJsScreenPath[] = "login.HostPairingScreen";
 
 const char kMethodContextChanged[] = "contextChanged";
 
+// Sent from JS when screen is ready to receive context updates.
+// TODO(dzhioev): Move 'contextReady' logic to the base screen handler when
+// all screens migrate to context-based communications.
+const char kCallbackContextReady[] = "contextReady";
+
 }  // namespace
 
 HostPairingScreenHandler::HostPairingScreenHandler()
-    : BaseScreenHandler(kJsScreenPath), delegate_(NULL), show_on_init_(false) {
+    : BaseScreenHandler(kJsScreenPath),
+      delegate_(NULL),
+      show_on_init_(false),
+      js_context_ready_(false) {
 }
 
 HostPairingScreenHandler::~HostPairingScreenHandler() {
   if (delegate_)
     delegate_->OnActorDestroyed(this);
 }
 
+void HostPairingScreenHandler::HandleContextReady() {
+  js_context_ready_ = true;
+  OnContextChanged(context_cache_.storage());
+}
+
 void HostPairingScreenHandler::Initialize() {
   if (!page_is_ready() || !delegate_)
     return;
 
   if (show_on_init_) {
     Show();
     show_on_init_ = false;
   }
 }
 
 void HostPairingScreenHandler::DeclareLocalizedValues(
     LocalizedValuesBuilder* builder) {
 }
 
 void HostPairingScreenHandler::RegisterMessages() {
+  AddPrefixedCallback(kCallbackContextReady,
+                      &HostPairingScreenHandler::HandleContextReady);
 }
 
 void HostPairingScreenHandler::Show() {
   if (!page_is_ready()) {
     show_on_init_ = true;
     return;
   }
   ShowScreen(OobeUI::kScreenHostPairing, NULL);
 }
 
 void HostPairingScreenHandler::Hide() {
 }
 
 void HostPairingScreenHandler::SetDelegate(Delegate* delegate) {
   delegate_ = delegate;
   if (page_is_ready())
     Initialize();
 }
 
 void HostPairingScreenHandler::OnContextChanged(
     const base::DictionaryValue& diff) {
+  if (!js_context_ready_) {
+    context_cache_.ApplyChanges(diff, NULL);
+    return;
+  }
   CallJS(kMethodContextChanged, diff);
 }
 
 }  // namespace chromeos