Remove redundant c_str() calls.

base/trace_event/trace_config.cc

Index: base/trace_event/trace_config.cc
diff --git a/base/trace_event/trace_config.cc b/base/trace_event/trace_config.cc
index 36de107bf8bc444426de0f16651306fb2a8d0b46..4f28d378fca4bb65cedc335ca70993d2757a8c1b 100644
--- a/base/trace_event/trace_config.cc
+++ b/base/trace_event/trace_config.cc
@@ -321,7 +321,7 @@ bool TraceConfig::IsCategoryGroupEnabled(
     DCHECK(!TraceConfig::IsEmptyOrContainsLeadingOrTrailingWhitespace(
                category_group_token))
         << "Disallowed category string";
-    if (IsCategoryEnabled(category_group_token.c_str()))
+    if (IsCategoryEnabled(category_group_token))
       return true;
 
     if (!MatchPattern(category_group_token, TRACE_DISABLED_BY_DEFAULT("*")))
@@ -855,7 +855,7 @@ void TraceConfig::WriteCategoryFilterString(const StringList& delays,
   }
 }
 
-bool TraceConfig::IsCategoryEnabled(const char* category_name) const {
+bool TraceConfig::IsCategoryEnabled(StringPiece category_name) const {
   // Check the disabled- filters and the disabled-* wildcard first so that a
   // "*" filter does not include the disabled.
   for (const std::string& category : disabled_categories_) {