[IndexedDB] Adding async tracing for renderer calls.

third_party/WebKit/Source/modules/indexeddb/IDBRequest.h

Index: third_party/WebKit/Source/modules/indexeddb/IDBRequest.h
diff --git a/third_party/WebKit/Source/modules/indexeddb/IDBRequest.h b/third_party/WebKit/Source/modules/indexeddb/IDBRequest.h
index 9f271b74ea499cc7318d796a7b5fdf5c67f007cd..de5141f6a5b1524964e6d077d65611bb1aaa556a 100644
--- a/third_party/WebKit/Source/modules/indexeddb/IDBRequest.h
+++ b/third_party/WebKit/Source/modules/indexeddb/IDBRequest.h
@@ -31,6 +31,7 @@
 
 #include <memory>
 
+#include "base/macros.h"
 #include "bindings/core/v8/ScriptValue.h"
 #include "core/dom/DOMStringList.h"
 #include "core/dom/SuspendableObject.h"
@@ -46,6 +47,7 @@
 #include "platform/blob/BlobData.h"
 #include "platform/heap/Handle.h"
 #include "platform/wtf/HashMap.h"
+#include "platform/wtf/Time.h"
 #include "public/platform/WebBlobInfo.h"
 #include "public/platform/modules/indexeddb/WebIDBCursor.h"
 #include "public/platform/modules/indexeddb/WebIDBTypes.h"
@@ -65,7 +67,28 @@ class MODULES_EXPORT IDBRequest : public EventTargetWithInlineData,
   USING_GARBAGE_COLLECTED_MIXIN(IDBRequest);
 
  public:
-  static IDBRequest* Create(ScriptState*, IDBAny* source, IDBTransaction*);
+  // Records async tracing, starting oncontruction and ending on destruction.

[pwnall, 2017/05/18 22:14:32]

onconstruction -> missing space?

[dmurph, 2017/05/18 23:51:15]

Done.

+  // UMA timing metrics are recorded on RecordUMAMetrics.
+  class ScopedMetricsTracker {
+   public:
+    ScopedMetricsTracker(const char* uma_name, const char* tracing_name, void*);
+    ~ScopedMetricsTracker();
+
+    void RecordUMAMetrics() const;
+
+   private:
+    const char* uma_name_ = nullptr;
+    const char* tracing_name_ = nullptr;
+    void* id_;
+    WTF::TimeTicks start_;
+
+    DISALLOW_COPY_AND_ASSIGN(ScopedMetricsTracker);
+  };
+
+  static IDBRequest* Create(ScriptState*,
+                            IDBAny* source,
+                            IDBTransaction*,
+                            std::unique_ptr<ScopedMetricsTracker>);
   ~IDBRequest() override;
   DECLARE_VIRTUAL_TRACE();
 
@@ -153,8 +176,16 @@ class MODULES_EXPORT IDBRequest : public EventTargetWithInlineData,
     transit_blob_handles_ = std::move(blob_handles);
   }
 
+  void AssignNewMetrics(std::unique_ptr<ScopedMetricsTracker> metrics) {
+    DCHECK(!metrics_);
+    metrics_ = std::move(metrics);
+  }
+
  protected:
-  IDBRequest(ScriptState*, IDBAny* source, IDBTransaction*);
+  IDBRequest(ScriptState*,
+             IDBAny* source,
+             IDBTransaction*,
+             std::unique_ptr<ScopedMetricsTracker>);
   void EnqueueEvent(Event*);
   void DequeueEvent(Event*);
   virtual bool ShouldEnqueueEvent() const;
@@ -180,12 +211,21 @@ class MODULES_EXPORT IDBRequest : public EventTargetWithInlineData,
   void AckReceivedBlobs(const IDBValue*);
   void AckReceivedBlobs(const Vector<RefPtr<IDBValue>>&);
 
+  void MaybeRecordMetrics() {

[pwnall, 2017/05/18 22:14:32]

metrics_ only seems to be null in testing.

1) Can this be RecordMetrics()? It seems to me that the testing situation is an
implementation detail.

2) How difficult would it be to pass non-null data all the time, so we don't
have separate code paths in unit tests vs everywhere else?

[dmurph, 2017/05/18 23:51:15]

Done.

+    if (metrics_) {
+      metrics_->RecordUMAMetrics();
+      metrics_.reset();
+    }
+  }
+
   void ClearPutOperationBlobs() { transit_blob_handles_.clear(); }
 
   Member<IDBAny> source_;
   Member<IDBAny> result_;
   Member<DOMException> error_;
 
+  std::unique_ptr<ScopedMetricsTracker> metrics_;
+
   bool has_pending_activity_ = true;
   HeapVector<Member<Event>> enqueued_events_;