Fix Clang-tidy readability-redundant-string-cstr warnings

Reviewers: zturner, labath

Subscribers: tberghammer, danalbert, lldb-commits
    
Differential Revision: https://reviews.llvm.org/D26233

llvm-svn: 285855
diff --git a/lldb/source/Core/StructuredData.cpp b/lldb/source/Core/StructuredData.cpp
index 46be782..48c368d 100644
--- a/lldb/source/Core/StructuredData.cpp
+++ b/lldb/source/Core/StructuredData.cpp
@@ -181,7 +181,7 @@
   if (this->GetType() == Type::eTypeDictionary) {
     std::pair<llvm::StringRef, llvm::StringRef> match = path.split('.');
     std::string key = match.first.str();
-    ObjectSP value = this->GetAsDictionary()->GetValueForKey(key.c_str());
+    ObjectSP value = this->GetAsDictionary()->GetValueForKey(key);
     if (value.get()) {
       // Do we have additional words to descend?  If not, return the
       // value we're at right now.