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

base/trace_event/trace_config.h

 // Copyright 2015 The Chromium 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 BASE_TRACE_EVENT_TRACE_CONFIG_H_
 #define BASE_TRACE_EVENT_TRACE_CONFIG_H_
 
 #include <stdint.h>
 
 #include <string>
@@ skipping 112 matching lines @@
   //           "periodic_interval_ms": 2000
   //         }
   //       ]
   //     }
   //   }
   //
   // Note: memory_dump_config can be specified only if
   // disabled-by-default-memory-infra category is enabled.
   explicit TraceConfig(const std::string& config_string);
 
+  // Create TraceConfig object from the trace config dictionary.

[Primiano Tucci (use gerrit), 2016/03/14 16:53:02]

I would probably reword this comment as:
// Functionally identical to the above, but takes a parsed dictionary as input
instead of its JSON serialization.

[Zhen Wang, 2016/03/14 21:41:45]

Done.

+  explicit TraceConfig(const base::DictionaryValue& config);

[Primiano Tucci (use gerrit), 2016/03/14 16:53:02]

nit: no need of base::, you are already in namespace base :)

[Primiano Tucci (use gerrit), 2016/03/14 16:53:02]

Since you introduced this, I think you can make a 2 line fix to
components/tracing/trace_config_file.cc.
That one is creating a DictionaryValue and serializing to JSON. THe latter does
not need to happen anymore thanks to your CL

[Primiano Tucci (use gerrit), 2016/03/14 16:53:02]

Can we haz a unittest to cover this casE?
I think you want to refactor some of the existing ones, so you can call them
either from the string or dictionary.

[Zhen Wang, 2016/03/14 21:41:45]

Updated trace_config_file.cc and trace_config_unittest.cc

+
   TraceConfig(const TraceConfig& tc);
 
   ~TraceConfig();
 
   TraceConfig& operator=(const TraceConfig& rhs);
 
   // Return a list of the synthetic delays specified in this category filter.
   const StringList& GetSyntheticDelayValues() const;
 
   TraceRecordMode GetTraceRecordMode() const { return record_mode_; }
@@ skipping 40 matching lines @@
                            IsEmptyOrContainsLeadingOrTrailingWhitespace);
   FRIEND_TEST_ALL_PREFIXES(TraceConfigTest, TraceConfigFromMemoryConfigString);
   FRIEND_TEST_ALL_PREFIXES(TraceConfigTest, LegacyStringToMemoryDumpConfig);
   FRIEND_TEST_ALL_PREFIXES(TraceConfigTest, EmptyMemoryDumpConfigTest);
 
   // The default trace config, used when none is provided.
   // Allows all non-disabled-by-default categories through, except if they end
   // in the suffix 'Debug' or 'Test'.
   void InitializeDefault();
 
-  // Initialize from the config string
+  // Initialize from the config dictionary.

[petrcermak, 2016/03/14 18:05:09]

supernit: s/the/a/

[Zhen Wang, 2016/03/14 21:41:45]

Done.

+  void InitializeFromConfigDict(const base::DictionaryValue& dict);

[Primiano Tucci (use gerrit), 2016/03/14 16:53:02]

nit, ditto: no need of base::

[Zhen Wang, 2016/03/14 21:41:45]

Done.

+
+  // Initialize from the config string.

[petrcermak, 2016/03/14 18:05:09]

ditto (s/the/a/)

[Zhen Wang, 2016/03/14 21:41:45]

Done.

   void InitializeFromConfigString(const std::string& config_string);
 
   // Initialize from category filter and trace options strings
   void InitializeFromStrings(const std::string& category_filter_string,
                              const std::string& trace_options_string);
 
   void SetCategoriesFromIncludedList(const base::ListValue& included_list);
   void SetCategoriesFromExcludedList(const base::ListValue& excluded_list);
   void SetSyntheticDelaysFromList(const base::ListValue& list);
   void AddCategoryToDict(base::DictionaryValue& dict,
@@ skipping 32 matching lines @@
   StringList included_categories_;
   StringList disabled_categories_;
   StringList excluded_categories_;
   StringList synthetic_delays_;
 };
 
 }  // namespace trace_event
 }  // namespace base
 
 #endif  // BASE_TRACE_EVENT_TRACE_CONFIG_H_