Revert "Revert "Add Atlas Text interface for rendering SDF glyphs.""

This reverts commit 9c2202ffc22b4293b48a4edeafa1b5d2bab8bb83.

Bug: skia:
Change-Id: I482ddf74f8e40d3d0908c840ba5c6ff981ccefbd
Reviewed-on: https://skia-review.googlesource.com/73345
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
diff --git a/gn/gpu.gni b/gn/gpu.gni
index e584bf5..a26111d 100644
--- a/gn/gpu.gni
+++ b/gn/gpu.gni
@@ -628,3 +628,14 @@
   "$_src/gpu/gl/iOS/GrGLCreateNativeInterface_iOS.cpp",
   "$_src/gpu/gl/android/GrGLCreateNativeInterface_android.cpp",
 ]
+
+skia_atlas_text_sources = [
+  "$_include/atlastext/SkAtlasTextContext.h",
+  "$_include/atlastext/SkAtlasTextFont.h",
+  "$_include/atlastext/SkAtlasTextRenderer.h",
+  "$_include/atlastext/SkAtlasTextTarget.h",
+
+  "$_src/atlastext/SkAtlasTextContext.cpp",
+  "$_src/atlastext/SkAtlasTextTarget.cpp",
+  "$_src/atlastext/SkInternalAtlasTextContext.cpp",
+]