Revert of Add builders for tracing event's structural arguments

base/debug/trace_event_impl.h

Index: base/debug/trace_event_impl.h
diff --git a/base/debug/trace_event_impl.h b/base/debug/trace_event_impl.h
index 146ca8f2aa55b545749e4d6cc520c8bc30431ccd..7b191b8a403f2bbf7baf25bde779ba691478db26 100644
--- a/base/debug/trace_event_impl.h
+++ b/base/debug/trace_event_impl.h
@@ -64,20 +64,13 @@
 
 // For any argument of type TRACE_VALUE_TYPE_CONVERTABLE the provided
 // class must implement this interface.
-class BASE_EXPORT ConvertableToTraceFormat
-    : public RefCounted<ConvertableToTraceFormat> {
+class ConvertableToTraceFormat : public RefCounted<ConvertableToTraceFormat> {
  public:
   // Append the class info to the provided |out| string. The appended
   // data must be a valid JSON object. Strings must be properly quoted, and
   // escaped. There is no processing applied to the content after it is
   // appended.
   virtual void AppendAsTraceFormat(std::string* out) const = 0;
-
-  std::string ToString() const {
-    std::string result;
-    AppendAsTraceFormat(&result);
-    return result;
-  }
 
  protected:
   virtual ~ConvertableToTraceFormat() {}