[WebAssembly] Return ArrayRef's rather than const std::vector&

[sbc100]

Summary

From working on lld I've learned this is generally the
preferred way for several reasons (e.g. more concise, improves
encapsulation).

[sbc100]

• revert parts

llvm/trunk/include/llvm/Object/Wasm.h

public:
   const wasm::WasmObjectHeader &getHeader() const;
   const WasmSymbol &getWasmSymbol(const DataRefImpl &Symb) const;
   const WasmSymbol &getWasmSymbol(const SymbolRef &Symbol) const;
   const WasmSection &getWasmSection(const SectionRef &Section) const;
   const wasm::WasmRelocation &getWasmRelocation(const RelocationRef& Ref) const;
 
   static bool classof(const Binary *v) { return v->isWasm(); }
 
-  const std::vector<wasm::WasmSignature>& types() const { return Signatures; }
-  const std::vector<uint32_t>& functionTypes() const { return FunctionTypes; }
-  const std::vector<wasm::WasmImport>& imports() const { return Imports; }
-  const std::vector<wasm::WasmTable>& tables() const { return Tables; }
-  const std::vector<wasm::WasmLimits>& memories() const { return Memories; }
-  const std::vector<wasm::WasmGlobal>& globals() const { return Globals; }
-  const std::vector<wasm::WasmExport>& exports() const { return Exports; }
+  ArrayRef<wasm::WasmSignature> types() const { return Signatures; }
+  ArrayRef<uint32_t> functionTypes() const { return FunctionTypes; }
+  ArrayRef<wasm::WasmImport> imports() const { return Imports; }
+  ArrayRef<wasm::WasmTable> tables() const { return Tables; }
+  ArrayRef<wasm::WasmLimits> memories() const { return Memories; }
+  ArrayRef<wasm::WasmGlobal> globals() const { return Globals; }
+  ArrayRef<wasm::WasmExport> exports() const { return Exports; }
   const wasm::WasmLinkingData& linkingData() const { return LinkingData; }
-
-  uint32_t getNumberOfSymbols() const {
-    return Symbols.size();
-  }
-
-  const std::vector<wasm::WasmElemSegment>& elements() const {
-    return ElemSegments;
-  }
-
-  const std::vector<WasmSegment>& dataSegments() const {
-    return DataSegments;
-  }
-
-  const std::vector<wasm::WasmFunction>& functions() const { return Functions; }
+  uint32_t getNumberOfSymbols() const { return Symbols.size(); }
+  ArrayRef<wasm::WasmElemSegment> elements() const { return ElemSegments; }
+  ArrayRef<WasmSegment> dataSegments() const { return DataSegments; }
+  ArrayRef<wasm::WasmFunction> functions() const { return Functions; }
   const ArrayRef<uint8_t>& code() const { return CodeSection; }
   uint32_t startFunction() const { return StartFunction; }
 
   void moveSymbolNext(DataRefImpl &Symb) const override;
 
   uint32_t getSymbolFlags(DataRefImpl Symb) const override;
 
   basic_symbol_iterator symbol_begin() const override;