rough unit test support for FM

I've punted for now on GPU test support.

Change-Id: I2ebe54a6fc61e1ce92120a6a221d5bb936b047e4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/255874
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index c034f53..e9ad6f4 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1755,6 +1755,7 @@
     }
     test_app("fm") {
       sources = [
+        "dm/DMGpuTestProcs.cpp",  # blech
         "tools/fm/fm.cpp",
       ]
       deps = [
@@ -1766,6 +1767,7 @@
         ":gpu_tool_utils",
         ":hash_and_encode",
         ":skia",
+        ":tests",
         ":tool_utils",
         ":trace",
         "modules/skottie",