Roll zlib to 646b7f569718921d7d4b5b8e22572ff6c76f2596.

Change-Id: I5c222fbacce6e89226d450534c7f9400cb6d2164
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/352044
Commit-Queue: Ryan Macnak <rmacnak@google.com>
Reviewed-by: Brian Quinlan <bquinlan@google.com>

Author: rmacnak-google

DEPS

@@ -111,7 +111,7 @@ vars = {
   "ply_rev": "604b32590ffad5cbb82e4afef1d305512d06ae93",
   "protobuf_gn_rev": "ca669f79945418f6229e4fef89b666b2a88cbb10",
   "WebCore_rev": "bcb10901266c884e7b3740abc597ab95373ab55c",
-  "zlib_rev": "14dd4c4455602c9b71a1a89b5cafd1f4030d2e3f",
+  "zlib_rev": "646b7f569718921d7d4b5b8e22572ff6c76f2596",
 
   ### /third_party/pkg dependencies
   # 'tools/rev_sdk_deps.dart' can rev pkg dependencies to their latest; put an

build/config/dcheck_always_on.gni

@@ -0,0 +1,8 @@
+# Copyright 2016 The Chromium Authors
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Compatiblity with Chromium's build for zlib.
+dcheck_is_configurable = false
+dcheck_always_on = false
+enable_expensive_dchecks = false