Add V8.ProduceCodeCache UMA

This CL adds V8.ProduceCodeCache UMA to measure the duration of
ProduceCacheInternal. This metric is only recorded when
ProduceCacheOptions is kProduceCodeCache. This metric can be useful to
estimate the impact of the CacheCodeOnIdle feature.

Bug: 1410082
Bug: 1260908
Change-Id: Ia90dce325961c2690a5c4bd20fb83ab5d33cc56a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4191623
Reviewed-by: Kenichi Ishibashi <bashi@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Hiroshige Hayashizaki <hiroshige@chromium.org>
Commit-Queue: Minoru Chikamune <chikamune@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1097708}

third_party/blink/renderer/bindings/core/v8/v8_code_cache.cc

@@ -4,6 +4,7 @@
 
 #include "third_party/blink/renderer/bindings/core/v8/v8_code_cache.h"
 
+#include "base/metrics/histogram_functions.h"
 #include "build/build_config.h"
 #include "third_party/abseil-cpp/absl/types/optional.h"
 #include "third_party/blink/public/mojom/v8_cache_options.mojom-blink.h"
@@ -234,6 +235,7 @@ static void ProduceCacheInternal(
       TRACE_EVENT_BEGIN1(kTraceEventCategoryGroup, trace_name, "fileName",
                          source_url.GetString().Utf8());
 
+      base::ElapsedTimer timer;
       std::unique_ptr<v8::ScriptCompiler::CachedData> cached_data(
           v8::ScriptCompiler::CreateCodeCache(unbound_script));
       if (cached_data) {
@@ -253,6 +255,7 @@ static void ProduceCacheInternal(
         cache_handler->SetCachedMetadata(
             code_cache_host, V8CodeCache::TagForCodeCache(cache_handler), data,
             length);
+        base::UmaHistogramTimes("V8.ProduceCodeCache", timer.Elapsed());
       }
 
       TRACE_EVENT_END1(kTraceEventCategoryGroup, trace_name, "data",

tools/metrics/histograms/metadata/v8/histograms.xml

@@ -1357,6 +1357,16 @@ chromium-metrics-reviews@google.com.
   </summary>
 </histogram>
 
+<histogram name="V8.ProduceCodeCache" units="ms" expires_after="2023-06-20">
+  <owner>chikamune@chromium.org</owner>
+  <owner>chrome-worker@google.com</owner>
+  <summary>
+    Time spent serializing and persisting code (mojo call) for V8 code caching.
+    Recorded when ProduceCacheInternal() is called. Only recorded when producing
+    a code cache is required.
+  </summary>
+</histogram>
+
 <histogram name="V8.RegExpBacktracks" units="backtracks"
     expires_after="2025-01-01">
   <owner>jgruber@chromium.org</owner>