[wasm] Cleanup AST decoder. Remove Tree and TreeResult.

test/unittests/wasm/ast-decoder-unittest.cc

 // Copyright 2015 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.
 
 #include "test/unittests/test-utils.h"
 
 #include "src/v8.h"
 
 #include "test/cctest/wasm/test-signatures.h"
 
@@ skipping 66 matching lines @@
   void AddLocals(LocalType type, uint32_t count) {
     local_decls.AddLocals(count, type);
   }
 
   // Prepends local variable declarations and renders nice error messages for
   // verification failures.
   void Verify(ErrorCode expected, FunctionSig* sig, const byte* start,
               const byte* end) {
     local_decls.Prepend(zone(), &start, &end);
     // Verify the code.
-    TreeResult result =
+    DecodeResult result =
         VerifyWasmCode(zone()->allocator(), module, sig, start, end);
 
     if (result.error_code != expected) {
       ptrdiff_t pc = result.error_pc - result.start;
       ptrdiff_t pt = result.error_pt - result.start;
       std::ostringstream str;
       if (expected == kSuccess) {
         str << "Verification failed: " << result.error_code << " pc = +" << pc;
         if (result.error_pt) str << ", pt = +" << pt;
         str << ", msg = " << result.error_msg.get();
@@ skipping 2335 matching lines @@
   LocalTypeMap map = Expand(decls);
   size_t pos = 0;
   pos = ExpectRun(map, pos, kAstF32, 5);
   pos = ExpectRun(map, pos, kAstI32, 1337);
   pos = ExpectRun(map, pos, kAstI64, 212);
 }
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8