Since we're only using it on Linux now, just require poppler as a system dependency.

DEPS

Index: DEPS
diff --git a/DEPS b/DEPS
index 55713a8ef7fa4f56490813fb37643c5e2b6ac6ce..c27c9a7a0f063e8a8a251e810fc1165744cd0e0d 100644
--- a/DEPS
+++ b/DEPS
@@ -12,16 +12,13 @@ deps = {
   # (see https://chromium.googlesource.com/chromium/chromium/+/c59bfa8ef877f45bfa859669053859857af1d279)
   "third_party/externals/angle" : "https://chromium.googlesource.com/external/angleproject.git",
   "third_party/externals/angle2" : "https://chromium.googlesource.com/angle/angle.git@bdc9b2f0ed9e365bf5a4d19799d93a512f07dd32",
-  "third_party/externals/fontconfig" : "https://skia.googlesource.com/third_party/fontconfig.git@2.11.0",
   "third_party/externals/freetype" : "https://skia.googlesource.com/third_party/freetype2.git@VER-2-5-0-1",
   "third_party/externals/gyp" : "https://chromium.googlesource.com/external/gyp.git@5917c6a6b77c9e97a0cbb66847194381bd36ec4c",
-  "third_party/externals/iconv" : "https://skia.googlesource.com/third_party/libiconv.git@v1.14",
   "third_party/externals/libjpeg" : "https://chromium.googlesource.com/chromium/deps/libjpeg_turbo.git@82ce8a6d4ebe12a177c0c3597192f2b4f09e81c3",
   "third_party/externals/jsoncpp" : "https://chromium.googlesource.com/external/jsoncpp/jsoncpp.git@ab1e40f3bce061ea6f9bdc60351d6cde2a4f872b",
   # Move to a webp version newer than 0.3.0 to pickup NEON fix for iOS
   "third_party/externals/jsoncpp-chromium" : "https://chromium.googlesource.com/chromium/src/third_party/jsoncpp.git@41239939c0c60481f34887d52c038facf05f5533",
   "third_party/externals/libwebp" : "https://chromium.googlesource.com/webm/libwebp.git@3fe91635df8734b23f3c1b9d1f0c4fa8cfaf4e39",
-  "third_party/externals/poppler" : "https://skia.googlesource.com/third_party/poppler.git@poppler-0.22.5",
   # "third_party/externals/v8" : "git://github.com/v8/v8.git@d15b0f0f2099dbd72867f3df70e9aaf5b8afbd2c",
 }