[wasm] [asm.js] Avoid expensive GetLineNumber up front in asm-typer.

src/asmjs/asm-typer.h

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SRC_ASMJS_ASM_TYPER_H_
 #define SRC_ASMJS_ASM_TYPER_H_
 
 #include <cstdint>
 #include <string>
+#include <unordered_map>
 #include <unordered_set>
 
 #include "src/allocation.h"
 #include "src/asmjs/asm-types.h"
 #include "src/ast/ast-type-bounds.h"
 #include "src/ast/ast-types.h"
 #include "src/ast/ast.h"
 #include "src/effects.h"
 #include "src/type-info.h"
 #include "src/zone/zone-containers.h"
@@ skipping 363 matching lines @@
   // the module name.
   VariableInfo* module_info_;
   Handle<String> module_name_;
 
   // 3 Environments
   ZoneHashMap global_scope_;  // 3.1 Global environment
   ZoneHashMap local_scope_;   // 3.2 Variable environment
 
   std::uintptr_t stack_limit_;
   bool stack_overflow_ = false;
-  ZoneMap<AstNode*, AsmType*> module_node_types_;
-  ZoneMap<AstNode*, AsmType*> function_node_types_;
+  std::unordered_map<AstNode*, AsmType*> module_node_types_;
+  std::unordered_map<AstNode*, AsmType*> function_node_types_;
   static const int kErrorMessageLimit = 128;
   AsmType* fround_type_;
   AsmType* ffi_type_;
   char error_message_[kErrorMessageLimit];
   StdlibSet stdlib_uses_;
 
   SourceLayoutTracker source_layout_;
   ReturnStatement* module_return_;
   ZoneVector<Assignment*> function_pointer_tables_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(AsmTyper);
 };
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
 
 #endif  // SRC_ASMJS_ASM_TYPER_H_