Use DCHECKs when observing only a single notification.

chrome/browser/file_select_helper.cc

 // Copyright (c) 2012 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/file_select_helper.h"
 
 #include <stddef.h>
 
 #include <string>
 #include <utility>
@@ skipping 610 matching lines @@
     return;
 
   render_frame_host_ = nullptr;
   web_contents_ = nullptr;
   Release();
 }
 
 void FileSelectHelper::EnumerateDirectory(int request_id,
                                           RenderViewHost* render_view_host,
                                           const base::FilePath& path) {
-
   // Because this class returns notifications to the RenderViewHost, it is
   // difficult for callers to know how long to keep a reference to this
   // instance. We AddRef() here to keep the instance alive after we return
   // to the caller, until the last callback is received from the enumeration
   // code. At that point, we must call EnumerateDirectoryEnd().
   AddRef();
   StartNewEnumeration(path, request_id, render_view_host);
 }
 
 // This method is called when we receive the last callback from the enumeration
 // code. Perform any cleanup and release the reference we added in
 // EnumerateDirectory().
 void FileSelectHelper::EnumerateDirectoryEnd() {
   Release();
 }
 
 void FileSelectHelper::Observe(int type,
                                const content::NotificationSource& source,
                                const content::NotificationDetails& details) {
-  switch (type) {
-    case content::NOTIFICATION_RENDER_WIDGET_HOST_DESTROYED: {
-      DCHECK(content::Source<RenderWidgetHost>(source).ptr() ==
-             render_frame_host_->GetRenderViewHost()->GetWidget());
-      render_frame_host_ = NULL;
-      break;
-    }
-    default:
-      NOTREACHED();
-  }
+  DCHECK_EQ(content::NOTIFICATION_RENDER_WIDGET_HOST_DESTROYED, type);
+  DCHECK_EQ(content::Source<RenderWidgetHost>(source).ptr(),
+            render_frame_host_->GetRenderViewHost()->GetWidget());
+  render_frame_host_ = nullptr;
 }
 
 void FileSelectHelper::RenderViewHostChanged(RenderViewHost* old_host,
                                              RenderViewHost* new_host) {
   CleanUpOnRenderViewHostChange();
 }
 
 void FileSelectHelper::WebContentsDestroyed() {
   web_contents_ = nullptr;
   CleanUpOnRenderViewHostChange();
@@ skipping 16 matching lines @@
 
 // static
 base::FilePath FileSelectHelper::GetSanitizedFileName(
     const base::FilePath& suggested_filename) {
   if (suggested_filename.empty())
     return base::FilePath();
   return net::GenerateFileName(
       GURL(), std::string(), std::string(), suggested_filename.AsUTF8Unsafe(),
       std::string(), l10n_util::GetStringUTF8(IDS_DEFAULT_DOWNLOAD_FILENAME));
 }