Initial switch to Chromium-style CHECK_* and DCHECK_* macros.

src/unique.h

Index: src/unique.h
diff --git a/src/unique.h b/src/unique.h
index 321eb3683dbedac418dd442c9d9f30ce9a9257ba..4c9a090f1548973214a79109d83a856f31e81c2c 100644
--- a/src/unique.h
+++ b/src/unique.h
@@ -49,7 +49,7 @@ class Unique {
       // TODO(titzer): other immortable immovable objects are also fine.
       DCHECK(!AllowHeapAllocation::IsAllowed() || handle->IsMap());
       raw_address_ = reinterpret_cast<Address>(*handle);
-      DCHECK_NE(raw_address_, NULL);  // Non-null should imply non-zero address.
+      DCHECK(raw_address_);  // Non-null should imply non-zero address.
     }
     handle_ = handle;
   }