Fix some defects identifies by Coverity Prevent. All are false...

src/zone.cc

Index: src/zone.cc
===================================================================
--- src/zone.cc	(revision 2520)
+++ src/zone.cc	(working copy)
@@ -176,7 +176,10 @@
     new_size = Max(kSegmentOverhead + size, kMaximumSegmentSize);
   }
   Segment* segment = Segment::New(new_size);
-  if (segment == NULL) V8::FatalProcessOutOfMemory("Zone");
+  if (segment == NULL) {
+    V8::FatalProcessOutOfMemory("Zone");
+    return NULL;
+  }
 
   // Recompute 'top' and 'limit' based on the new segment.
   Address result = RoundUp(segment->start(), kAlignment);