add a SkFontMgr to DM that returns portable fonts

Controlled by --[no]nativeFonts, and still defaults to native fonts.

Change-Id: Ib2879e69fadb63ddb5a17a7e4ae227941893b8cf
Reviewed-on: https://skia-review.googlesource.com/67806
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
diff --git a/BUILD.gn b/BUILD.gn
index 3cf2352..e7744c9 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1340,6 +1340,7 @@
     test_app("dm") {
       sources = [
         "dm/DM.cpp",
+        "dm/DMFontMgr.cpp",
         "dm/DMGpuTestProcs.cpp",
         "dm/DMJsonWriter.cpp",
         "dm/DMSrcSink.cpp",