[WebAssembly] Return a StringRef instead of std::string from getSectionName(). NFC.

[ruiu]

Summary

[WebAssembly] Return a StringRef instead of std::string from getSectionName(). NFC.

wasm/OutputSections.h

 class OutputSegment;
 
 class OutputSection {
 public:
   OutputSection(uint32_t Type, std::string Name = "")
       : Type(Type), Name(Name) {}
   virtual ~OutputSection() = default;
 
-  std::string getSectionName() const;
+  StringRef getSectionName() const;
   void setOffset(size_t NewOffset) {
     log("setOffset: " + toString(*this) + ": " + Twine(NewOffset));
     Offset = NewOffset;
   }
   void createHeader(size_t BodySize);
   virtual size_t getSize() const = 0;
   virtual void writeTo(uint8_t *Buf) = 0;
   virtual void finalizeContents() {}

wasm/OutputSections.cpp

case WASM_SEC_CODE:
     return "CODE";
   case WASM_SEC_DATA:
     return "DATA";
   default:
     fatal("invalid section type");
   }
 }
 
-std::string lld::toString(const OutputSection &Section) {
-  std::string rtn = Section.getSectionName();
-  if (!Section.Name.empty())
-    rtn += "(" + Section.Name + ")";
-  return rtn;
+// Returns a string, e.g. "FUNCTION(.text)".
+std::string lld::toString(const OutputSection &Sec) {
+  if (!Sec.Name.empty())
+    return (Sec.getSectionName() + "(" + Sec.Name + ")").str();
+  return Sec.getSectionName();
 }
 
-std::string OutputSection::getSectionName() const {
+StringRef OutputSection::getSectionName() const {
   return sectionTypeToString(Type);
 }
 
 void OutputSection::createHeader(size_t BodySize) {
   raw_string_ostream OS(Header);
-  debugWrite(OS.tell(), "section type [" + Twine(getSectionName()) + "]");
+  debugWrite(OS.tell(), "section type [" + getSectionName() + "]");
   encodeULEB128(Type, OS);
   writeUleb128(OS, BodySize, "section size");
   OS.flush();
   log("createHeader: " + toString(*this) + " body=" + Twine(BodySize) +
       " total=" + Twine(getSize()));
 }
 
 CodeSection::CodeSection(ArrayRef<InputFunction *> Functions)