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 504 matching lines @@
 
   resourceRequest.setAllowStoredCredentials(
       request.options().allowCredentials == AllowStoredCredentials);
   return Continue;
 }
 
 Resource* ResourceFetcher::requestResource(
     FetchRequest& request,
     const ResourceFactory& factory,
     const SubstituteData& substituteData) {
-  unsigned long identifier = createUniqueIdentifier();
   ResourceRequest& resourceRequest = request.mutableResourceRequest();
+  unsigned browserGeneratedRequestId =
+      resourceRequest.browserGeneratedRequestId();
+
+  // If set browserGeneratedRequestId should be an odd number.
+  DCHECK(browserGeneratedRequestId == 0 || browserGeneratedRequestId & 1);
+  // We use even numbers for blink generated fetch identifiers so we can
+  // distinguish between them and make sure there are no collisions.
+  unsigned long identifier = browserGeneratedRequestId
+                                 ? browserGeneratedRequestId
+                                 : createUniqueIdentifier() * 2;
   network_instrumentation::ScopedResourceLoadTracker scopedResourceLoadTracker(
       identifier, resourceRequest);
   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 blockedReason =
       ResourceRequestBlockedReason::None;
@@ skipping 1015 matching lines @@
   visitor->trace(m_context);
   visitor->trace(m_archive);
   visitor->trace(m_loaders);
   visitor->trace(m_nonBlockingLoaders);
   visitor->trace(m_documentResources);
   visitor->trace(m_preloads);
   visitor->trace(m_resourceTimingInfoMap);
 }
 
 }  // namespace blink