NTP: Sync shown sections across instances

This adds a pref observer for prefs::kNTPShownSections and calls a js function when these changes. This is so that instances of the NTP do not get out of sync with each other.

BUG=None
TEST=Open two or more NTPs. Hide and show different sections and the sections should be hidden and removed on all instances.

Review URL: http://codereview.chromium.org/2792004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@49487 0039d316-1c4b-4281-b951-d872f2087c98

5 files changed, 61 insertions, 13 deletions

diff --git a/chrome/browser/dom_ui/new_tab_ui.cc b/chrome/browser/dom_ui/new_tab_ui.cc
index 097c8b7..8bcb449 100644
--- a/chrome/browser/dom_ui/new_tab_ui.cc
+++ b/chrome/browser/dom_ui/new_tab_ui.cc
@@ -458,7 +458,8 @@ NewTabUI::NewTabUI(TabContents* contents)
   }
 
   if (!GetProfile()->IsOffTheRecord()) {
-    AddMessageHandler((new ShownSectionsHandler())->Attach(this));
+    PrefService* pref_service = GetProfile()->GetPrefs();
+    AddMessageHandler((new ShownSectionsHandler(pref_service))->Attach(this));
     AddMessageHandler((new MostVisitedHandler())->Attach(this));
     AddMessageHandler((new RecentlyClosedTabsHandler())->Attach(this));
     AddMessageHandler((new MetricsHandler())->Attach(this));
diff --git a/chrome/browser/dom_ui/shown_sections_handler.cc b/chrome/browser/dom_ui/shown_sections_handler.cc
index ecc8f1b..aad15014 100644
--- a/chrome/browser/dom_ui/shown_sections_handler.cc
+++ b/chrome/browser/dom_ui/shown_sections_handler.cc
@@ -13,6 +13,8 @@
 #include "chrome/browser/profile.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/extensions/extension.h"
+#include "chrome/common/notification_details.h"
+#include "chrome/common/notification_type.h"
 #include "chrome/common/pref_names.h"
 
 namespace {
@@ -39,6 +41,15 @@ void NotifySectionDisabled(int new_mode, int old_mode, Profile *profile) {
 
 }  // namespace
 
+ShownSectionsHandler::ShownSectionsHandler(PrefService* pref_service)
+    : pref_service_(pref_service) {
+  pref_service_->AddPrefObserver(prefs::kNTPShownSections, this);
+}
+
+ShownSectionsHandler::~ShownSectionsHandler() {
+  pref_service_->RemovePrefObserver(prefs::kNTPShownSections, this);
+}
+
 void ShownSectionsHandler::RegisterMessages() {
   dom_ui_->RegisterMessageCallback("getShownSections",
       NewCallback(this, &ShownSectionsHandler::HandleGetShownSections));
@@ -46,10 +57,21 @@ void ShownSectionsHandler::RegisterMessages() {
       NewCallback(this, &ShownSectionsHandler::HandleSetShownSections));
 }
 
+void ShownSectionsHandler::Observe(NotificationType type,
+                                   const NotificationSource& source,
+                                   const NotificationDetails& details) {
+  DCHECK(NotificationType::PREF_CHANGED == type);
+  std::wstring* pref_name = Details<std::wstring>(details).ptr();
+  DCHECK(*pref_name == prefs::kNTPShownSections);
+
+  int sections = pref_service_->GetInteger(prefs::kNTPShownSections);
+  FundamentalValue sections_value(sections);
+  dom_ui_->CallJavascriptFunction(L"setShownSections", sections_value);
+}
+
 void ShownSectionsHandler::HandleGetShownSections(const Value* value) {
-  PrefService* pref_service = dom_ui_->GetProfile()->GetPrefs();
-  SetFirstAppLauncherRunPref(pref_service);
-  int sections = pref_service->GetInteger(prefs::kNTPShownSections);
+  SetFirstAppLauncherRunPref(pref_service_);
+  int sections = pref_service_->GetInteger(prefs::kNTPShownSections);
   FundamentalValue sections_value(sections);
   dom_ui_->CallJavascriptFunction(L"onShownSections", sections_value);
 }
@@ -72,13 +94,11 @@ void ShownSectionsHandler::HandleSetShownSections(const Value* value) {
   DCHECK(r) << "Missing value in setShownSections from the NTP Most Visited.";
 
   int mode = StringToInt(mode_string);
-  int old_mode = dom_ui_->GetProfile()->GetPrefs()->GetInteger(
-      prefs::kNTPShownSections);
+  int old_mode = pref_service_->GetInteger(prefs::kNTPShownSections);
 
   if (old_mode != mode) {
     NotifySectionDisabled(mode, old_mode, dom_ui_->GetProfile());
-    dom_ui_->GetProfile()->GetPrefs()->SetInteger(
-        prefs::kNTPShownSections, mode);
+    pref_service_->SetInteger(prefs::kNTPShownSections, mode);
   }
 }
 
diff --git a/chrome/browser/dom_ui/shown_sections_handler.h b/chrome/browser/dom_ui/shown_sections_handler.h
index 32cc70c..804c368 100644
--- a/chrome/browser/dom_ui/shown_sections_handler.h
+++ b/chrome/browser/dom_ui/shown_sections_handler.h
@@ -6,6 +6,7 @@
 #define CHROME_BROWSER_DOM_UI_SHOWN_SECTIONS_HANDLER_H_
 
 #include "chrome/browser/dom_ui/dom_ui.h"
+#include "chrome/common/notification_observer.h"
 
 class DOMUI;
 class Value;
@@ -21,14 +22,20 @@ enum Section {
   DEBUG = 32
 };
 
-class ShownSectionsHandler : public DOMMessageHandler {
+class ShownSectionsHandler : public DOMMessageHandler,
+                             public NotificationObserver {
  public:
-  ShownSectionsHandler() {}
-  virtual ~ShownSectionsHandler() {}
+  explicit ShownSectionsHandler(PrefService* pref_service);
+  virtual ~ShownSectionsHandler();
 
   // DOMMessageHandler implementation.
   virtual void RegisterMessages();
 
+  // NotificationObserver implementation.
+  virtual void Observe(NotificationType type,
+                       const NotificationSource& source,
+                       const NotificationDetails& details);
+
   // Callback for "getShownSections" message.
   void HandleGetShownSections(const Value* value);
 
@@ -45,6 +52,8 @@ class ShownSectionsHandler : public DOMMessageHandler {
                                int new_pref_version);
 
  private:
+  PrefService* pref_service_;
+
   DISALLOW_COPY_AND_ASSIGN(ShownSectionsHandler);
 };
 
diff --git a/chrome/browser/resources/new_new_tab.html b/chrome/browser/resources/new_new_tab.html
index 3be5df2..b29a3fa 100644
--- a/chrome/browser/resources/new_new_tab.html
+++ b/chrome/browser/resources/new_new_tab.html
@@ -52,6 +52,7 @@ registerCallback('syncMessageChanged');
 registerCallback('tips');
 registerCallback('onHomePageSet');
 registerCallback('getAppsCallback');
+registerCallback('setShownSections');
 
 </script>
 <!-- template data placeholder -->
diff --git a/chrome/browser/resources/new_new_tab.js b/chrome/browser/resources/new_new_tab.js
index 16d47b7..8fc13a7 100644
--- a/chrome/browser/resources/new_new_tab.js
+++ b/chrome/browser/resources/new_new_tab.js
@@ -239,7 +239,9 @@ function getSectionElement(section) {
 function showSection(section) {
   if (!(section & shownSections)) {
     shownSections |= section;
-    getSectionElement(section).classList.remove('hidden');
+    var el = getSectionElement(section);
+    if (el)
+      el.classList.remove('hidden');
 
     switch (section) {
       case Section.THUMB:
@@ -267,7 +269,22 @@ function hideSection(section) {
         break;
     }
 
-    getSectionElement(section).classList.add('hidden');
+    var el = getSectionElement(section);
+    if (el)
+      el.classList.add('hidden');
+  }
+}
+
+/**
+ * Callback when the shown sections changes in another NTP.
+ * @param {number} newShownSections Bitmask of the shown sections.
+ */
+function setShownSections(newShownSections) {
+  for (var key in Section) {
+    if (newShownSections & Section[key])
+      showSection(Section[key]);
+    else
+      hideSection(Section[key]);
   }
 }