Fix default category filter for tracing

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 57e61781d7e09c893a2415af0c35538d4f6cd7a0..73db56a7ef7d9f913cf13ff68f189753eb4f148a 100644
--- a/base/trace_event/trace_config.h
+++ b/base/trace_event/trace_config.h
@@ -188,7 +188,8 @@ class BASE_EXPORT TraceConfig {
   std::string ToCategoryFilterString() const;
 
   // Returns true if at least one category in the list is enabled by this
-  // trace config.
+  // trace config. This is used to determine if the category filters are
+  // enabled in the TRACE_* macros.
   bool IsCategoryGroupEnabled(const char* category_group) const;
 
   // Merges config with the current TraceConfig
@@ -207,7 +208,6 @@ class BASE_EXPORT TraceConfig {
   FRIEND_TEST_ALL_PREFIXES(TraceConfigTest, TraceConfigFromValidLegacyFormat);
   FRIEND_TEST_ALL_PREFIXES(TraceConfigTest,
                            TraceConfigFromInvalidLegacyStrings);
-  FRIEND_TEST_ALL_PREFIXES(TraceConfigTest, ConstructDefaultTraceConfig);
   FRIEND_TEST_ALL_PREFIXES(TraceConfigTest, TraceConfigFromValidString);
   FRIEND_TEST_ALL_PREFIXES(TraceConfigTest, TraceConfigFromInvalidString);
   FRIEND_TEST_ALL_PREFIXES(TraceConfigTest,
@@ -215,6 +215,8 @@ class BASE_EXPORT TraceConfig {
   FRIEND_TEST_ALL_PREFIXES(TraceConfigTest, TraceConfigFromMemoryConfigString);
   FRIEND_TEST_ALL_PREFIXES(TraceConfigTest, LegacyStringToMemoryDumpConfig);
   FRIEND_TEST_ALL_PREFIXES(TraceConfigTest, EmptyMemoryDumpConfigTest);
+  FRIEND_TEST_ALL_PREFIXES(TraceConfigTest,
+                           EmptyAndAsteriskCategoryFilterString);
 
   // The default trace config, used when none is provided.
   // Allows all non-disabled-by-default categories through, except if they end
@@ -253,7 +255,9 @@ class BASE_EXPORT TraceConfig {
   void WriteCategoryFilterString(const StringList& delays,
                                  std::string* out) const;
 
-  // Returns true if category is enable according to this trace config.
+  // Returns true if the category is enable according to this trace config.

[Primiano Tucci (use gerrit), 2016/06/14 15:13:03]

since you are touching this line: s/enable/enabled/ :)

[Zhen Wang, 2016/06/14 20:55:08]

Done.

+  // This is only used internally. Please refer to IsCategoryGroupEnabled()

[Primiano Tucci (use gerrit), 2016/06/14 15:13:02]

Well it's not that this is internal. It's more that this tells whether a
category is enabled from the traceconfig perspective.
THe other in TraceLog tells whether the category is enabled from the tracing
runtime perspective.
The real problem here is that some of the logic (the *) happens only in the
TraceLog

[Zhen Wang, 2016/06/14 20:55:08]

Updated.

+  // when determining the enabled category filters.
   bool IsCategoryEnabled(const char* category_name) const;
 
   static bool IsEmptyOrContainsLeadingOrTrailingWhitespace(