Run clang-modernize -use-nullptr over src/extensions/.

extensions/browser/app_window/app_window_registry.cc

Index: extensions/browser/app_window/app_window_registry.cc
diff --git a/extensions/browser/app_window/app_window_registry.cc b/extensions/browser/app_window/app_window_registry.cc
index 9cd72e967d5cd56cd09f78d23d600b73b5aae222..1390dbd4ab7ab773bae093eb78c9bdca8dd9682b 100644
--- a/extensions/browser/app_window/app_window_registry.cc
+++ b/extensions/browser/app_window/app_window_registry.cc
@@ -151,7 +151,7 @@ AppWindow* AppWindowRegistry::GetAppWindowForRenderViewHost(
       return *i;
   }
 
-  return NULL;
+  return nullptr;
 }
 
 AppWindow* AppWindowRegistry::GetAppWindowForNativeWindow(
@@ -163,12 +163,12 @@ AppWindow* AppWindowRegistry::GetAppWindowForNativeWindow(
       return *i;
   }
 
-  return NULL;
+  return nullptr;
 }
 
 AppWindow* AppWindowRegistry::GetCurrentAppWindowForApp(
     const std::string& app_id) const {
-  AppWindow* result = NULL;
+  AppWindow* result = nullptr;
   for (AppWindowList::const_iterator i = app_windows_.begin();
        i != app_windows_.end();
        ++i) {
@@ -185,7 +185,7 @@ AppWindow* AppWindowRegistry::GetCurrentAppWindowForApp(
 AppWindow* AppWindowRegistry::GetAppWindowForAppAndKey(
     const std::string& app_id,
     const std::string& window_key) const {
-  AppWindow* result = NULL;
+  AppWindow* result = nullptr;
   for (AppWindowList::const_iterator i = app_windows_.begin();
        i != app_windows_.end();
        ++i) {
@@ -223,7 +223,7 @@ AppWindow* AppWindowRegistry::GetAppWindowForNativeWindowAnyProfile(
       return app_window;
   }
 
-  return NULL;
+  return nullptr;
 }
 
 // static