[gin] Plumb TraceLogStateObserver into v8.

gin/public/v8_platform.h

Index: gin/public/v8_platform.h
diff --git a/gin/public/v8_platform.h b/gin/public/v8_platform.h
index ad37a5c4cebf7b519cad0885c5fa17526cc297f4..2dd32a055570bf2c0e985a9365eb32af27882784 100644
--- a/gin/public/v8_platform.h
+++ b/gin/public/v8_platform.h
@@ -49,6 +49,9 @@ class GIN_EXPORT V8Platform : public NON_EXPORTED_BASE(v8::Platform) {
                                 const char* name,
                                 uint64_t handle) override;
 
+  void AddTraceStateObserver(v8::Platform::TraceStateObserver*) override;
+  void RemoveTraceStateObserver(v8::Platform::TraceStateObserver*) override;
+
  private:
   friend struct base::DefaultLazyInstanceTraits<V8Platform>;