Fix realloc to not call the new_handler (which is for failures)...

third_party/tcmalloc/allocator_shim.cc

Index: third_party/tcmalloc/allocator_shim.cc
===================================================================
--- third_party/tcmalloc/allocator_shim.cc	(revision 25582)
+++ third_party/tcmalloc/allocator_shim.cc	(working copy)
@@ -160,7 +160,11 @@
     // TCMalloc case.
     new_ptr = do_realloc(ptr, size);
 #endif
-    if (new_ptr)
+
+    // Subtle warning:  NULL return does not alwas indicate out-of-memory.  If
+    // the requested new size is zero, realloc should free the ptr and return
+    // NULL.
+    if (new_ptr || !size)
       return new_ptr;
     if (!new_mode || !call_new_handler(true))
       break;