Plumbing devtools agent host id and request id between processes

third_party/WebKit/Source/platform/loader/fetch/ResourceFetcher.cpp

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller (mueller@kde.org)
     Copyright (C) 2002 Waldo Bastian (bastian@kde.org)
     Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All
     rights reserved.
     Copyright (C) 2009 Torch Mobile Inc. http://www.torchmobile.com/
 
     This library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Library General Public
@@ skipping 529 matching lines @@
 
   resource_request.SetAllowStoredCredentials(
       request.Options().allow_credentials == kAllowStoredCredentials);
   return kContinue;
 }
 
 Resource* ResourceFetcher::RequestResource(
     FetchRequest& request,
     const ResourceFactory& factory,
     const SubstituteData& substitute_data) {
-  unsigned long identifier = CreateUniqueIdentifier();
   ResourceRequest& resource_request = request.MutableResourceRequest();
+  int browser_generated_request_id =
+      resource_request.BrowserGeneratedRequestId();
+
+  // If set browser_generated_request_id should be a negative number
+  DCHECK_LE(browser_generated_request_id, 0);
+  // We use positive numbers for blink generated fetch identifiers so we can
+  // distinguish between them and make sure there are no collisions.
+  unsigned long identifier =
+      browser_generated_request_id
+          ? static_cast<unsigned long>(browser_generated_request_id) &
+                0xFFFFFFFF
+          : CreateUniqueIdentifier();
   network_instrumentation::ScopedResourceLoadTracker
       scoped_resource_load_tracker(identifier, resource_request);
   SCOPED_BLINK_UMA_HISTOGRAM_TIMER("Blink.Fetch.RequestResourceTime");
   // TODO(dproy): Remove this. http://crbug.com/659666
   TRACE_EVENT1("blink", "ResourceFetcher::requestResource", "url",
                UrlForTraceEvent(request.Url()));
 
   Resource* resource = nullptr;
   ResourceRequestBlockedReason blocked_reason =
       ResourceRequestBlockedReason::kNone;
@@ skipping 1015 matching lines @@
   visitor->Trace(context_);
   visitor->Trace(archive_);
   visitor->Trace(loaders_);
   visitor->Trace(non_blocking_loaders_);
   visitor->Trace(document_resources_);
   visitor->Trace(preloads_);
   visitor->Trace(resource_timing_info_map_);
 }
 
 }  // namespace blink