Roll third_party/zlib/ 646b7f569..3787595bb (4 commits)

https://chromium.googlesource.com/chromium/src/third_party/zlib.git/+log/646b7f569718..3787595bbbd3

Created with:
  roll-dep third_party/zlib

Change-Id: Ifdc680e33813e56f659cc7614bded758fce9a5e8
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/117070
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Thomas Sepez <tsepez@google.com>
Commit-Queue: Lei Zhang <thestig@chromium.org>
diff --git a/DEPS b/DEPS
index b1f12ee..b65a041 100644
--- a/DEPS
+++ b/DEPS
@@ -203,7 +203,7 @@
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling zlib
   # and whatever else without interference from each other.
-  'zlib_revision': '646b7f569718921d7d4b5b8e22572ff6c76f2596',
+  'zlib_revision': '3787595bbbd3a374613713164db935e8331f5825',
 }
 
 # Only these hosts are allowed for dependencies in this DEPS file.