Revert of [tracing] Support ConvertableToTraceFormat argument type.

src/libplatform/default-platform.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_LIBPLATFORM_DEFAULT_PLATFORM_H_
 #define V8_LIBPLATFORM_DEFAULT_PLATFORM_H_
 
 #include <functional>
 #include <map>
 #include <queue>
@@ skipping 33 matching lines @@
                               ExpectedRuntime expected_runtime) override;
   void CallOnForegroundThread(v8::Isolate* isolate, Task* task) override;
   void CallDelayedOnForegroundThread(Isolate* isolate, Task* task,
                                      double delay_in_seconds) override;
   void CallIdleOnForegroundThread(Isolate* isolate, IdleTask* task) override;
   bool IdleTasksEnabled(Isolate* isolate) override;
   double MonotonicallyIncreasingTime() override;
   const uint8_t* GetCategoryGroupEnabled(const char* name) override;
   const char* GetCategoryGroupName(
       const uint8_t* category_enabled_flag) override;
-  uint64_t AddTraceEvent(
-      char phase, const uint8_t* category_enabled_flag, const char* name,
-      const char* scope, uint64_t id, uint64_t bind_id, int32_t num_args,
-      const char** arg_names, const uint8_t* arg_types,
-      const uint64_t* arg_values,
-      std::unique_ptr<v8::ConvertableToTraceFormat>* arg_convertables,
-      unsigned int flags) override;
+  uint64_t AddTraceEvent(char phase, const uint8_t* category_enabled_flag,
+                         const char* name, const char* scope, uint64_t id,
+                         uint64_t bind_id, int32_t num_args,
+                         const char** arg_names, const uint8_t* arg_types,
+                         const uint64_t* arg_values,
+                         unsigned int flags) override;
   void UpdateTraceEventDuration(const uint8_t* category_enabled_flag,
                                 const char* name, uint64_t handle) override;
   void SetTracingController(tracing::TracingController* tracing_controller);
 
  private:
   static const int kMaxThreadPoolSize;
 
   Task* PopTaskInMainThreadQueue(v8::Isolate* isolate);
   Task* PopTaskInMainThreadDelayedQueue(v8::Isolate* isolate);
 
@@ skipping 13 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(DefaultPlatform);
 };
 
 
 }  // namespace platform
 }  // namespace v8
 
 
 #endif  // V8_LIBPLATFORM_DEFAULT_PLATFORM_H_