Roll DEPS for zlib to 8c371ad7

https://chromium.googlesource.com/chromium/src/third_party/zlib.git/+log/91155b5d..8c371ad7

TBR=dsinclair@chromium.org

Change-Id: I11bf8537e4cd5032da4b0f5dcc0ff31ac15db83c
Reviewed-on: https://pdfium-review.googlesource.com/28771
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
diff --git a/DEPS b/DEPS
index 681d913..b9f3c5a 100644
--- a/DEPS
+++ b/DEPS
@@ -34,7 +34,7 @@
   'trace_event_revision': '0e9a47d74970bee1bbfc063c47215406f8918699',
   'v8_revision': '9cf8abb7ce7e3a3152fb71d0e87678e64f7ab0c8',
   'yasm_source_revision': 'b98114e18d8b9b84586b10d24353ab8616d4c5fc',
-  'zlib_revision': '91155b5d0737713fc7f0499cf0ba2c4f2af24014',
+  'zlib_revision': '8c371ad77b836c02e44006dc2dc77c5d6d910861',
 }
 
 deps = {