Merge to XFA: Re-enable pdfium_unittests.

Original CL at https://codereview.chromium.org/835233002

R=brucedawson@chromium.org

Review URL: https://codereview.chromium.org/810153005
diff --git a/DEPS b/DEPS
index b5fbbb2..1f73277 100644
--- a/DEPS
+++ b/DEPS
@@ -2,6 +2,9 @@
   "build/gyp":
     "https://chromium.googlesource.com/external/gyp",
 
+  "testing/gtest":
+     "https://chromium.googlesource.com/external/googletest.git@8245545b6dc9c4703e6496d1efd19e975ad2b038",
+
   "v8":
     "https://chromium.googlesource.com/external/v8",