[cleanup] Use for..of and nullptr in devtools ui bindings

R=yangguo@chromium.org

Change-Id: I6930da9f938db2f3bfe4c5062dce30fc4847f3a6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2401037
Auto-Submit: Simon Zünd <szuend@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#805691}

chrome/browser/devtools/devtools_ui_bindings.cc

@@ -171,7 +171,7 @@ Browser* FindBrowser(content::WebContents* web_contents) {
     if (tab_index != TabStripModel::kNoTab)
       return browser;
   }
-  return NULL;
+  return nullptr;
 }
 
 // DevToolsUIDefaultDelegate --------------------------------------------------
@@ -658,14 +658,14 @@ void DevToolsUIBindings::FrontendWebContentsObserver::DidFinishNavigation(
 DevToolsUIBindings* DevToolsUIBindings::ForWebContents(
      content::WebContents* web_contents) {
   if (!g_devtools_ui_bindings_instances.IsCreated())
-    return NULL;
+    return nullptr;
   DevToolsUIBindingsList* instances =
       g_devtools_ui_bindings_instances.Pointer();
-  for (auto it(instances->begin()); it != instances->end(); ++it) {
-    if ((*it)->web_contents() == web_contents)
-      return *it;
+  for (DevToolsUIBindings* binding : *instances) {
+    if (binding->web_contents() == web_contents)
+      return binding;
   }
-  return NULL;
+  return nullptr;
 }
 
 DevToolsUIBindings::DevToolsUIBindings(content::WebContents* web_contents)