Add MalDocA source code to third_party directory.

Following third_party approval process outlined at https://chromium.googlesource.com/chromium/src.git/+/HEAD/docs/adding_to_third_party.md
to add MalDocA to Chromium's third_party directory. This library will be
utilized to extend the capabilities of Safe Browsing Download Protection
through the analysis of macros from Office documents

Bug: 1188201
Change-Id: I3bc863bb0ee54f733773264ad50d15ba8441dd00
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2958804
Reviewed-by: Chris Palmer <palmer@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@google.com>
Reviewed-by: Charlie Reis <creis@chromium.org>
Commit-Queue: Olabode O. Anise II <anise@chromium.org>
Cr-Commit-Position: refs/heads/master@{#904426}
NOKEYCHECK=True
GitOrigin-RevId: d42a4b66900280f8488a921dd0dd05f96ee7a814
diff --git a/BUILD.gn b/BUILD.gn
index 8068e57..5ade3ef 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -142,6 +142,7 @@
     "//third_party/blink/renderer/*",
     "//third_party/fontconfig",
     "//third_party/libxslt",
+    "//third_party/maldoca/*",
   ]
   if (is_ios) {
     foreach(tgt, ios_libxml_visibility_additions) {