Fix DCHECK with unsigned int in zone.cc.

src/zone.cc

Index: src/zone.cc
diff --git a/src/zone.cc b/src/zone.cc
index 5a7245bd44b86a53bc52c19a445b38ed156d92f4..9dcebba2dc1fc8fee3fd4c5fd363e6f55b3b47c0 100644
--- a/src/zone.cc
+++ b/src/zone.cc
@@ -264,8 +264,8 @@ Address Zone::NewExpand(size_t size) {
   // Check for address overflow.
   // (Should not happen since the segment is guaranteed to accomodate
   // size bytes + header and alignment padding)
-  DCHECK_GE(reinterpret_cast<uintptr_t>(position_),
-            reinterpret_cast<uintptr_t>(result));
+  DCHECK(reinterpret_cast<uintptr_t>(position_) >=
+         reinterpret_cast<uintptr_t>(result));
   limit_ = segment->end();
   DCHECK(position_ <= limit_);
   return result;