Update DevTools Tracing.Start to accept trace config as a parameter

base/trace_event/trace_config.h

Index: base/trace_event/trace_config.h
diff --git a/base/trace_event/trace_config.h b/base/trace_event/trace_config.h
index 81b7d515133dd0c3c71f461316ced768e6fd9618..8ea249502d641919adbda0fb620f58814fffa803 100644
--- a/base/trace_event/trace_config.h
+++ b/base/trace_event/trace_config.h
@@ -130,6 +130,9 @@ class BASE_EXPORT TraceConfig {
   // disabled-by-default-memory-infra category is enabled.
   explicit TraceConfig(const std::string& config_string);
 
+  // Create TraceConfig object from the trace config dictionary.
+  explicit TraceConfig(const base::DictionaryValue& config);
+
   TraceConfig(const TraceConfig& tc);
 
   ~TraceConfig();
@@ -190,7 +193,10 @@ class BASE_EXPORT TraceConfig {
   // in the suffix 'Debug' or 'Test'.
   void InitializeDefault();
 
-  // Initialize from the config string
+  // Initialize from the config dictionary.
+  void InitializeFromConfigDict(const base::DictionaryValue& dict);
+
+  // Initialize from the config string.
   void InitializeFromConfigString(const std::string& config_string);
 
   // Initialize from category filter and trace options strings