Patch adding detail to perf measures

performance-measure.patch

diff --git a/third_party/blink/renderer/core/timing/performance_user_timing.cc b/third_party/blink/renderer/core/timing/performance_user_timing.cc
index 1056e5c6f04d7..3f7a36ba36450 100644
--- a/third_party/blink/renderer/core/timing/performance_user_timing.cc
+++ b/third_party/blink/renderer/core/timing/performance_user_timing.cc
@@ -210,12 +210,28 @@ PerformanceMeasure* UserTiming::Measure(ScriptState* script_state,
     WTF::AddFloatToHash(hash, start_time);
     WTF::AddFloatToHash(hash, end_time);
 
+    v8::Local<v8::Context> context =
+        performance_->GetExecutionContext()->GetIsolate()->GetCurrentContext();
+    String serialized_detail = "";
+    if (!detail.V8Value()->IsNullOrUndefined()) {
+      v8::Local<v8::String> v8_string;
+      if (v8::JSON::Stringify(context, detail.V8Value()).ToLocal(&v8_string)) {
+        serialized_detail = ToCoreString(v8_string);
+      }
+    }
+
     TRACE_EVENT_COPY_NESTABLE_ASYNC_BEGIN_WITH_TIMESTAMP1(
         "blink.user_timing", measure_name.Utf8().c_str(), hash,
         unsafe_start_time, "startTime", start_time);
-    TRACE_EVENT_COPY_NESTABLE_ASYNC_END_WITH_TIMESTAMP0(
-        "blink.user_timing", measure_name.Utf8().c_str(), hash,
-        unsafe_end_time);
+    if (serialized_detail.length()) {
+      TRACE_EVENT_NESTABLE_ASYNC_END_WITH_TIMESTAMP1(
+          "blink.user_timing", measure_name.Utf8().c_str(), hash,
+          unsafe_end_time, "serialized_detail", serialized_detail);
+    } else {
+      TRACE_EVENT_NESTABLE_ASYNC_END_WITH_TIMESTAMP0(
+          "blink.user_timing", measure_name.Utf8().c_str(), hash,
+          unsafe_end_time);
+    }
   }
 
   PerformanceMeasure* measure =
diff --git a/third_party/blink/web_tests/inspector-protocol/timeline/user-timing-expected.txt b/third_party/blink/web_tests/inspector-protocol/timeline/user-timing-expected.txt
index 022ce7fb3734a..cbeea2b596e39 100644
--- a/third_party/blink/web_tests/inspector-protocol/timeline/user-timing-expected.txt
+++ b/third_party/blink/web_tests/inspector-protocol/timeline/user-timing-expected.txt
@@ -1,14 +1,17 @@
 Tests render blocking status in script traces.
 Recording started
 Tracing complete
+first to third
+"detail of first to third"
+first to third-2
+{"name":"test","v":1}
+first to third-2
+first to third
 now to first
 now
 now to first
 first to second
-first to third
 first
 first to second
 second
-first to third
 third
-
diff --git a/third_party/blink/web_tests/inspector-protocol/timeline/user-timing.js b/third_party/blink/web_tests/inspector-protocol/timeline/user-timing.js
index cbb8fc54cbc55..674cb05887f90 100644
--- a/third_party/blink/web_tests/inspector-protocol/timeline/user-timing.js
+++ b/third_party/blink/web_tests/inspector-protocol/timeline/user-timing.js
@@ -23,17 +23,24 @@
         performance.mark("third");
         performance.measure("now to first", "now", "first");
         performance.measure("first to second", "first", "second");
-        performance.measure("first to third", "first", "third");
+        performance.measure("first to third", {
+          detail: "detail of first to third",
+          start: 10, end: 25});
+        performance.measure("first to third-2", {
+          detail: {name: "test", v: 1},
+          start: 20, end: 25});
     })();
   `);
 
   const events = await tracingHelper.stopTracing(/blink.user_timing/);
   const sorted_events = events.sort((a, b) => {
-    return (a["ts"] - b["ts"]);
+    return a["ts"] - b["ts"];
   });
 
   for (let e of sorted_events) {
     testRunner.log(e["name"]);
+    if (e.args?.["serialized_detail"])
+      testRunner.log(e.args?.["serialized_detail"]);
   }
 
   testRunner.completeTest();