[DevTools] Only create DevToolsAgent for local main frame.

content/renderer/render_frame_impl.cc

 // Copyright 2013 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 "content/renderer/render_frame_impl.h"
 
 #include <map>
 #include <string>
 
 #include "base/auto_reset.h"
@@ skipping 3203 matching lines @@
 
 void RenderFrameImpl::didFinishResourceLoad(blink::WebLocalFrame* frame,
                                             unsigned identifier) {
   DCHECK(!frame_ || frame_ == frame);
   InternalDocumentStateData* internal_data =
       InternalDocumentStateData::FromDataSource(frame->dataSource());
   if (!internal_data->use_error_page())
     return;
 
   // Do not show error page when DevTools is attached.
-  if (render_view_->devtools_agent_->IsAttached())
+  if (render_view_->devtools_agent_ &&
+      render_view_->devtools_agent_->IsAttached()) {
     return;
+  }
 
   // Display error page, if appropriate.
   std::string error_domain = "http";
   int http_status_code = internal_data->http_status_code();
   if (GetContentClient()->renderer()->HasErrorPage(
           http_status_code, &error_domain)) {
     WebURLError error;
     error.unreachableURL = frame->document().url();
     error.domain = WebString::fromUTF8(error_domain);
     error.reason = http_status_code;
@@ skipping 1303 matching lines @@
 
 #if defined(ENABLE_BROWSER_CDMS)
 RendererCdmManager* RenderFrameImpl::GetCdmManager() {
   if (!cdm_manager_)
     cdm_manager_ = new RendererCdmManager(this);
   return cdm_manager_;
 }
 #endif  // defined(ENABLE_BROWSER_CDMS)
 
 }  // namespace content