ChromeDriver should be able to focus on a frame using its frame element,

chrome/test/webdriver/dispatch.cc

 // Copyright (c) 2010 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/test/webdriver/dispatch.h"
 
 #include <sstream>
 #include <string>
 #include <vector>
 
@@ skipping 41 matching lines @@
 
 void Shutdown(struct mg_connection* connection,
               const struct mg_request_info* request_info,
               void* user_data) {
   base::WaitableEvent* shutdown_event =
       reinterpret_cast<base::WaitableEvent*>(user_data);
   mg_printf(connection, "HTTP/1.1 200 OK\r\n\r\n");
   shutdown_event->Signal();
 }
 
+void SendNoContentResponse(struct mg_connection* connection,
+                           const struct mg_request_info* request_info,
+                           void* user_data) {
+  std::string response = "HTTP/1.1 204 No Content\r\n"
+                         "Content-Length:0\r\n"
+                         "\r\n";
+  mg_write(connection, response.data(), response.length());
+}
+
 void SendNotImplementedError(struct mg_connection* connection,
                              const struct mg_request_info* request_info,
                              void* user_data) {
   // Send a well-formed WebDriver JSON error response to ensure clients
   // handle it correctly.
   std::string body = base::StringPrintf(
       "{\"status\":%d,\"value\":{\"message\":"
       "\"Command has not been implemented yet: %s %s\"}}",
       kUnknownCommand, request_info->request_method, request_info->uri);
 
@@ skipping 166 matching lines @@
     response->SetValue(methods);
     return;
   }
 
   DispatchCommand(command.get(), method, response);
 }
 
 }  // namespace internal
 
 Dispatcher::Dispatcher(struct mg_context* context, const std::string& root)
-    : context_(context), root_(root) {}
+    : context_(context), root_(root) {
+  // Overwrite mongoose's default handler for /favicon.ico to always return a
+  // 204 response so we don't spam the logs with 404s.
+  mg_set_uri_callback(context_, "/favicon.ico", &SendNoContentResponse, NULL);
+}
 
 Dispatcher::~Dispatcher() {}
 
 void Dispatcher::AddShutdown(const std::string& pattern,
                              base::WaitableEvent* shutdown_event) {
   mg_set_uri_callback(context_, (root_ + pattern).c_str(), &Shutdown,
                       shutdown_event);
 }
 
 void Dispatcher::SetNotImplemented(const std::string& pattern) {
   mg_set_uri_callback(context_, (root_ + pattern).c_str(),
                       &SendNotImplementedError, NULL);
 }
 
 }  // namespace webdriver