[Demangle] replace use of llvm::StringView w/ std::string_view

This refactoring was waiting on converting LLVM to C++17.

Leave StringView.h and cleanup around for subsequent cleanup.

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D148384

Author: nickdesaulniers

lldb/source/Plugins/SymbolFile/NativePDB/PdbAstBuilder.cpp

@@ -25,6 +25,7 @@
 #include "UdtRecordCompleter.h"
 #include "SymbolFileNativePDB.h"
 #include <optional>
+#include <string_view>
 
 using namespace lldb_private;
 using namespace lldb_private::npdb;
@@ -174,7 +175,7 @@ PdbAstBuilder::CreateDeclInfoForType(const TagRecord &record, TypeIndex ti) {
     return CreateDeclInfoForUndecoratedName(record.Name);
 
   llvm::ms_demangle::Demangler demangler;
-  StringView sv(record.UniqueName.begin(), record.UniqueName.size());
+  std::string_view sv(record.UniqueName.begin(), record.UniqueName.size());
   llvm::ms_demangle::TagTypeNode *ttn = demangler.parseTagUniqueName(sv);
   if (demangler.Error)
     return {m_clang.GetTranslationUnitDecl(), std::string(record.UniqueName)};

lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.cpp

@@ -57,6 +57,7 @@
 #include "PdbUtil.h"
 #include "UdtRecordCompleter.h"
 #include <optional>
+#include <string_view>
 
 using namespace lldb;
 using namespace lldb_private;
@@ -631,7 +632,7 @@ static std::string GetUnqualifiedTypeName(const TagRecord &record) {
   }
 
   llvm::ms_demangle::Demangler demangler;
-  StringView sv(record.UniqueName.begin(), record.UniqueName.size());
+  std::string_view sv(record.UniqueName.begin(), record.UniqueName.size());
   llvm::ms_demangle::TagTypeNode *ttn = demangler.parseTagUniqueName(sv);
   if (demangler.Error)
     return std::string(record.Name);