tracing: Report ResourceClients and the reason for not deletable for web-caches

third_party/WebKit/Source/core/loader/DocumentThreadableLoader.h

Index: third_party/WebKit/Source/core/loader/DocumentThreadableLoader.h
diff --git a/third_party/WebKit/Source/core/loader/DocumentThreadableLoader.h b/third_party/WebKit/Source/core/loader/DocumentThreadableLoader.h
index 5e62f1a696e51085347fd035f6bacc09684cada9..dd691c59819e40d8952879a2cd74f6ccf7dc20dd 100644
--- a/third_party/WebKit/Source/core/loader/DocumentThreadableLoader.h
+++ b/third_party/WebKit/Source/core/loader/DocumentThreadableLoader.h
@@ -81,6 +81,8 @@ class CORE_EXPORT DocumentThreadableLoader final : public ThreadableLoader, priv
         // |this| may be dead after calling this method.
         void notifyFinished(Resource*) override;
 
+        String debugName() const override { return "DocumentThreadableLoader"; }
+
         // RawResourceClient
         //
         // |this| may be dead after calling these methods.