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 4082416fc77e0cde2093ea85a53f2ffe82b85583..3d9b06cbe8738b542e9b6229318e4468ba12f7db 100644
--- a/third_party/WebKit/Source/platform/loader/fetch/ResourceFetcher.cpp
+++ b/third_party/WebKit/Source/platform/loader/fetch/ResourceFetcher.cpp
@@ -522,8 +522,17 @@ 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");