Subzero: Fix compilation error in MINIMAL=1 or NOASSERT=1 mode.

BUG= none
R=jpp@chromium.org

Review URL: https://codereview.chromium.org/1182673003
diff --git a/src/IceAssembler.h b/src/IceAssembler.h
index 55ef088..69faa95 100644
--- a/src/IceAssembler.h
+++ b/src/IceAssembler.h
@@ -96,8 +96,8 @@
 
   public:
     explicit EnsureCapacity(AssemblerBuffer *Buffer) {
-      if (Buffer->cursor() >= buffer->limit())
-        buffer->extendCapacity();
+      if (Buffer->cursor() >= Buffer->limit())
+        Buffer->extendCapacity();
     }
   };