Fix warnings on Win64.

test/cctest/test-heap.cc

Index: test/cctest/test-heap.cc
diff --git a/test/cctest/test-heap.cc b/test/cctest/test-heap.cc
index 9911ce42bc12db47c5991b3d97de71eb4f92ac6b..fb9a48e790274812bfadff16d6e726197df5855e 100644
--- a/test/cctest/test-heap.cc
+++ b/test/cctest/test-heap.cc
@@ -262,7 +262,7 @@ TEST(GarbageCollection) {
 
 static void VerifyStringAllocation(const char* string) {
   String* s = String::cast(Heap::AllocateStringFromUtf8(CStrVector(string)));
-  CHECK_EQ(static_cast<int>(strlen(string)), s->length());
+  CHECK_EQ(StrLength(string), s->length());
   for (int index = 0; index < s->length(); index++) {
     CHECK_EQ(static_cast<uint16_t>(string[index]), s->Get(index));  }
 }
@@ -285,7 +285,7 @@ TEST(LocalHandles) {
   v8::HandleScope scope;
   const char* name = "Kasper the spunky";
   Handle<String> string = Factory::NewStringFromAscii(CStrVector(name));
-  CHECK_EQ(static_cast<int>(strlen(name)), string->length());
+  CHECK_EQ(StrLength(name), string->length());
 }