[wasm] Fix more -Wsign-compare warnings.

test/cctest/wasm/wasm-run-utils.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 WASM_RUN_UTILS_H
 #define WASM_RUN_UTILS_H
 
 #include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
@@ skipping 81 matching lines @@
     if (instance->mem_start) {
       free(instance->mem_start);
     }
     if (interpreter_) delete interpreter_;
   }
 
   void ChangeOriginToAsmjs() { origin = kAsmJsOrigin; }
 
   byte* AddMemory(uint32_t size) {
     CHECK_NULL(instance->mem_start);
-    CHECK_EQ(0, instance->mem_size);
+    CHECK_EQ(0u, instance->mem_size);
     instance->mem_start = reinterpret_cast<byte*>(malloc(size));
     CHECK(instance->mem_start);
     memset(instance->mem_start, 0, size);
     instance->mem_size = size;
     return raw_mem_start<byte>();
   }
 
   template <typename T>
   T* AddMemoryElems(uint32_t count) {
     AddMemory(count * sizeof(T));
@@ skipping 676 matching lines @@
 // interpreter.
 #define WASM_EXEC_TEST(name)                                               \
   void RunWasm_##name(WasmExecutionMode execution_mode);                   \
   TEST(RunWasmCompiled_##name) { RunWasm_##name(kExecuteCompiled); }       \
   TEST(RunWasmInterpreted_##name) { RunWasm_##name(kExecuteInterpreted); } \
   void RunWasm_##name(WasmExecutionMode execution_mode)
 
 }  // namespace
 
 #endif