Revert "core: allow building against system zlib"

This reverts commit 36c5b170e722362d4b5f7cb6e4e0099ed227a307.

Reason for revert: This appears to be blocking the roll into Chromium.
https://chromium-review.googlesource.com/c/476165/



Original change's description:
> core: allow building against system zlib
> 
> In a way similar to the existing USE_SYSTEM_LIBJPEG. The default is of
> course still the DEPS-based zlib checkout.
> 
> Change-Id: I649e75beb1a19c4cf7abda42fa10ebe5babfe946
> Reviewed-on: https://pdfium-review.googlesource.com/4070
> Reviewed-by: Lei Zhang <thestig@chromium.org>
> Commit-Queue: Lei Zhang <thestig@chromium.org>
> 

TBR=thestig@chromium.org,dsinclair@chromium.org,npm@chromium.org,vmiklos@collabora.co.uk,pdfium-reviews@googlegroups.com
# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: I1ee6fb002f444ff9b559ce6a69679e63de7ff9cc
Reviewed-on: https://pdfium-review.googlesource.com/4393
Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: dsinclair <dsinclair@chromium.org>

5 files changed, 4 insertions, 27 deletions

diff --git a/AUTHORS b/AUTHORS
index 7499c1094c..6c2a295990 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -36,7 +36,6 @@ Robert Sesek <rsesek@chromium.org>
 Sam Clegg <sbc@chromium.org>
 Thomas Sepez <tsepez@chromium.org>
 
-Collabora Ltd. <*@collabora.co.uk>
 DocsCorp Pty Ltd. <*@docscorp.com>
 Foxit Software Inc <*@foxitsoftware.com>
 Google Inc. <*@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index ab221062ae..34480246cf 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -703,7 +703,7 @@ static_library("fxcodec") {
     "third_party:fx_lcms2",
     "third_party:fx_libopenjpeg",
     "//third_party:jpeg",
-    "//third_party:zlib",
+    "//third_party/zlib:zlib",
   ]
 
   if (pdf_enable_xfa) {
diff --git a/core/fxcodec/codec/fx_codec_flate.cpp b/core/fxcodec/codec/fx_codec_flate.cpp
index 5af3e99c2e..4d1e034a23 100644
--- a/core/fxcodec/codec/fx_codec_flate.cpp
+++ b/core/fxcodec/codec/fx_codec_flate.cpp
@@ -15,12 +15,7 @@
 #include "core/fxcrt/fx_extension.h"
 #include "third_party/base/numerics/safe_conversions.h"
 #include "third_party/base/ptr_util.h"
-
-#if defined(USE_SYSTEM_ZLIB)
-#include <zlib.h>
-#else
 #include "third_party/zlib/zlib.h"
-#endif
 
 extern "C" {
 
diff --git a/skia/BUILD.gn b/skia/BUILD.gn
index 74546ebfc0..d4a837191d 100644
--- a/skia/BUILD.gn
+++ b/skia/BUILD.gn
@@ -317,7 +317,7 @@ component("skia") {
   deps = [
     ":skia_opts",
     "//:freetype_common",
-    "//third_party:zlib",
+    "//third_party/zlib:zlib",
   ]
 
   if (is_linux) {
diff --git a/third_party/BUILD.gn b/third_party/BUILD.gn
index 17c9c22832..c270a1063a 100644
--- a/third_party/BUILD.gn
+++ b/third_party/BUILD.gn
@@ -288,8 +288,6 @@ if (!build_with_chromium) {
     # Uses libjpeg_turbo as the jpeg implementation. Has no effect if
     # use_system_libjpeg is set.
     use_libjpeg_turbo = true
-
-    use_system_zlib = false
   }
 
   config("system_libjpeg_config") {
@@ -318,21 +316,6 @@ if (!build_with_chromium) {
       ]
     }
   }
-
-  config("system_zlib_config") {
-    libs = [ "z" ]
-    defines = [ "USE_SYSTEM_ZLIB" ]
-  }
-
-  group("zlib") {
-    if (use_system_zlib) {
-      public_configs = [ ":system_zlib_config" ]
-    } else {
-      public_deps = [
-        "//third_party/zlib",
-      ]
-    }
-  }
 }
 
 config("fx_libopenjpeg_warnings") {
@@ -412,7 +395,7 @@ static_library("fx_lpng") {
   defines = []
   cflags = []
   deps = [
-    "//third_party:zlib",
+    "//third_party/zlib",
   ]
 
   if (current_cpu == "x86" || current_cpu == "x64") {
@@ -452,7 +435,7 @@ if (pdf_enable_xfa) {
     }
     deps = [
       "//third_party:jpeg",
-      "//third_party:zlib",
+      "//third_party/zlib",
     ]
     sources = [
       "libtiff/tif_aux.c",