chrome: Fix callbacks for different Profile types (see issue #2969)

- Only install network intercepts for Profiles that have an associated
  CefBrowserContext. For incognito windows the CefBrowserContext is
  associated with the OffTheRecordProfileImpl's original Profile.
- cefsimple: Return the default CefClient instance for browser windows
  created via the Chrome UI, and allow Chrome to show error pages.

tests/cefsimple/simple_app.cc

@@ -85,8 +85,7 @@ void SimpleApp::OnContextInitialized() {
   CefRefPtr<CefCommandLine> command_line =
       CefCommandLine::GetGlobalCommandLine();
 
-  const bool enable_chrome_runtime =
-      command_line->HasSwitch("enable-chrome-runtime");
+  const bool enable_chrome_runtime = SimpleHandler::IsChromeRuntimeEnabled();
 
 #if defined(OS_WIN) || defined(OS_LINUX)
   // Create the browser using the Views framework if "--use-views" is specified
@@ -135,3 +134,8 @@ void SimpleApp::OnContextInitialized() {
                                   nullptr, nullptr);
   }
 }
+
+CefRefPtr<CefClient> SimpleApp::GetDefaultClient() {
+  // Called when a new browser window is created via the Chrome runtime UI.
+  return SimpleHandler::GetInstance();
+}