clean up drawTextUTF8 and rename to textToGlyphRunList

Pull out the glyph positioning code in anticipations of removing
simplifyDrawText.

This is part of a larger CL:
https://skia-review.googlesource.com/c/skia/+/388719

Change-Id: I935fd91f70d708a7a30785b6eea8e4e7c1f9c739
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/392416
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Herb Derby <herb@google.com>
diff --git a/src/gpu/ops/GrAtlasTextOp.cpp b/src/gpu/ops/GrAtlasTextOp.cpp
index 5745d52..dcaf5e3 100644
--- a/src/gpu/ops/GrAtlasTextOp.cpp
+++ b/src/gpu/ops/GrAtlasTextOp.cpp
@@ -497,9 +497,7 @@
     drawMatrix.preTranslate(x, y);
     auto drawOrigin = SkPoint::Make(x, y);
     SkGlyphRunBuilder builder;
-    builder.drawTextUTF8(font, text, textLen, drawOrigin);
-
-    auto glyphRunList = builder.useGlyphRunList();
+    auto glyphRunList = builder.textToGlyphRunList(font, text, textLen, drawOrigin);
     if (glyphRunList.empty()) {
         return nullptr;
     }