Remove TraceOptions string based constructor.

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 ab5d09e9d97ce9753ea933afafb39fe9fc9a3bb4..4cbb72144739043fe7a25f348dd6fc572ce722d5 100644
--- a/base/debug/trace_event_impl.h
+++ b/base/debug/trace_event_impl.h
@@ -409,11 +409,21 @@ struct BASE_EXPORT TraceOptions {
   // options_string, the last one takes precedence. If none of the trace
   // recording mode is specified, recording mode is RECORD_UNTIL_FULL.
   //
-  // Example: TraceOptions("record-until-full")
-  // Example: TraceOptions("record-continuously, enable-sampling")
-  // Example: TraceOptions("record-until-full, trace-to-console") would have
-  //          ECHO_TO_CONSOLE as the recording mode.
-  explicit TraceOptions(const std::string& options_string);
+  // The trace option will first be reset to the default option
+  // (record_mode set to RECORD_UNTIL_FULL, enable_sampling and enable_systrace
+  // set to false) before options parsed from |options_string| are applied on
+  // it.
+  // If |options_string| is invalid, the final state of trace_options is
+  // undefined.
+  //
+  // Example: trace_options.SetFromString("record-until-full")
+  // Example: trace_options.SetFromString(
+  //              "record-continuously, enable-sampling")
+  // Example: trace_options.SetFromString("record-until-full, trace-to-console")
+  // will set ECHO_TO_CONSOLE as the recording mode.
+  //
+  // Returns true on success.
+  bool SetFromString(const std::string& options_string);
 
   std::string ToString() const;