Add IsCloningDataFinishedBeforeResponseComplete histogram

This is a follow up for crrev.com/c/6101238. To ensure if the
speculative fix introduced in crrev.com/c/6101238 actually works, and
understand how often the case happens, this CL adds the new boolean
metrics.

Bug: 384414080
Change-Id: I25d75a1408a69b5fe4752b9714913084308eeb17
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6096624
Reviewed-by: Takashi Toyoshima <toyoshim@chromium.org>
Reviewed-by: Keita Suzuki <suzukikeita@chromium.org>
Commit-Queue: Shunya Shishido <sisidovski@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1397774}

content/common/service_worker/race_network_request_url_loader_client.cc

@@ -33,6 +33,17 @@ const char kMainResourceHistogramForRaceNetworkFetchEvent[] =
     "ServiceWorker.FetchEvent.MainResource.RaceNetworkRequest";
 const char kSubresourceHistogramForRaceNetworkFetchEvent[] =
     "ServiceWorker.FetchEvent.Subresource.RaceNetworkRequest";
+
+void RecordRaceNetworkRequestCloningResponseForFetchHandlerHistogram(
+    bool is_main_resource,
+    bool is_cloning_data_finished_before_response_complete) {
+  base::UmaHistogramBoolean(
+      base::StrCat({is_main_resource
+                        ? kMainResourceHistogramForRaceNetworkFetchEvent
+                        : kSubresourceHistogramForRaceNetworkFetchEvent,
+                    ".IsCloningDataFinishedBeforeResponseComplete"}),
+      is_cloning_data_finished_before_response_complete);
+}
 }  // namespace
 
 ServiceWorkerRaceNetworkRequestURLLoaderClient::
@@ -382,6 +393,9 @@ void ServiceWorkerRaceNetworkRequestURLLoaderClient::CompleteResponse() {
     // ServiceWorkerStaticRouterRaceNetworkRequestPerformanceImprovement feature
     // is enabled.
     forwarding_client_->OnComplete(completion_status_.value());
+    RecordRaceNetworkRequestCloningResponseForFetchHandlerHistogram(
+        is_main_resource_,
+        /*is_cloning_data_finished_before_response_complete=*/true);
   }
 }
 
@@ -689,6 +703,9 @@ void ServiceWorkerRaceNetworkRequestURLLoaderClient::
     // completed as well.
     forwarding_client_->OnComplete(completion_status_.value());
     write_buffer_manager_for_fetch_handler_.ResetProducer();
+    RecordRaceNetworkRequestCloningResponseForFetchHandlerHistogram(
+        is_main_resource_,
+        /*is_cloning_data_finished_before_response_complete=*/false);
   }
 }
 

tools/metrics/histograms/metadata/service/histograms.xml

@@ -456,6 +456,25 @@ chromium-metrics-reviews@google.com.
   </token>
 </histogram>
 
+<histogram
+    name="ServiceWorker.FetchEvent.{Resource}.RaceNetworkRequest.IsCloningDataFinishedBeforeResponseComplete"
+    enum="Boolean" expires_after="2025-05-11">
+  <owner>sisidovski@chromium.org</owner>
+  <owner>chrome-worker@google.com</owner>
+  <summary>
+    Recorded as true when the data cloning from the original response to the
+    data pipe for the fetch handler is completed, but still the completion
+    status via `ServiceWorkerRaceNetworkRequestURLLoaderClient::OnComplete()` is
+    not invoked.
+
+    This metric is recorded per {Resource}.
+  </summary>
+  <token key="Resource">
+    <variant name="MainResource" summary="main resource"/>
+    <variant name="Subresource" summary="subresource"/>
+  </token>
+</histogram>
+
 <histogram
     name="ServiceWorker.FetchEvent.{Resource}.RaceNetworkRequest.Redirect"
     enum="Boolean" expires_after="2025-01-26">