Add animated text samples

BUG=skia:

Change-Id: I0b0a00a0d5c5790a1fc963458bc90c968830afd8
Reviewed-on: https://skia-review.googlesource.com/8361
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Mike Reed <reed@google.com>
diff --git a/gn/samples.gni b/gn/samples.gni
index 0fd0df9..7f8f3b9 100644
--- a/gn/samples.gni
+++ b/gn/samples.gni
@@ -67,6 +67,7 @@
   "$_samplecode/SampleMegaStroke.cpp",
   "$_samplecode/SamplePatch.cpp",
   "$_samplecode/SamplePath.cpp",
+  "$_samplecode/SamplePathText.cpp",
   "$_samplecode/SamplePathClip.cpp",
   "$_samplecode/SamplePathEffects.cpp",
   "$_samplecode/SamplePathFuzz.cpp",