WebUI: Vulcanize MD Downloads at compile time using GN.

Deletes 240kb, 3400LOC of checked in generated code.

BUG=673825
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2569293002
Cr-Commit-Position: refs/heads/master@{#445934}
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index cd54fcc..1b7d34b 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -4143,6 +4143,10 @@
     "//url/mojo:url_mojom_origin__generator",
   ]
 
+  if (use_vulcanize) {
+    deps += [ "//chrome/browser/resources/md_downloads:vulcanize" ]
+  }
+
   if (safe_browsing_mode > 0) {
     deps +=
         [ "//chrome/browser/resources/safe_browsing:make_file_types_protobuf" ]