[wasm] Fix more -Wsign-compare warnings.

test/cctest/wasm/test-run-wasm-js.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 <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
 #include "src/wasm/wasm-macro-gen.h"
@@ skipping 411 matching lines @@
   ADD_CODE(code, kExprCallFunction, 0);
 
   size_t end = code.size();
   code.push_back(0);
 
   // Call different select JS functions.
   for (int which = 0; which < num_params; which++) {
     HandleScope scope(isolate);
     TestingModule module;
     uint32_t js_index = AddJSSelector(&module, &sig, which);
-    CHECK_EQ(0, js_index);
+    CHECK_EQ(0u, js_index);
     WasmFunctionCompiler t(&sig, &module);
     t.Build(&code[0], &code[end]);
 
     Handle<JSFunction> jsfunc = module.WrapCode(t.CompileAndAdd());
 
     Handle<Object> args[] = {
         factory->NewNumber(inputs.arg_d(0)),
         factory->NewNumber(inputs.arg_d(1)),
         factory->NewNumber(inputs.arg_d(2)),
         factory->NewNumber(inputs.arg_d(3)),
@@ skipping 65 matching lines @@
   RunJSSelectAlignTest(9, 9);
 }
 
 TEST(Run_JSSelectAlign_10) {
   CcTest::InitializeVM();
   RunJSSelectAlignTest(10, 7);
   RunJSSelectAlignTest(10, 8);
   RunJSSelectAlignTest(10, 9);
   RunJSSelectAlignTest(10, 10);
 }