Plumbing devtools agent host id and request id between processes

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

Index: third_party/WebKit/Source/platform/loader/fetch/ResourceFetcher.cpp
diff --git a/third_party/WebKit/Source/platform/loader/fetch/ResourceFetcher.cpp b/third_party/WebKit/Source/platform/loader/fetch/ResourceFetcher.cpp
index e17a24a7547d7b7344346c6ae243950ca2102002..84ea48e3072389bc35b764b69224bc6f97a586ec 100644
--- a/third_party/WebKit/Source/platform/loader/fetch/ResourceFetcher.cpp
+++ b/third_party/WebKit/Source/platform/loader/fetch/ResourceFetcher.cpp
@@ -547,8 +547,19 @@ 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");