Replace all uses of GrSlug with sktext::gpu::Slug

Follow-up to http://review.skia.org/542300

Change-Id: I1deb65fb4788325fe2ecbe632ca7719d6f1d84dd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4605336
Commit-Queue: Kevin Lubick <kjlubick@chromium.org>
Reviewed-by: Florin Malita <fmalita@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1155745}

diff --git a/cc/raster/gpu_raster_buffer_provider.cc b/cc/raster/gpu_raster_buffer_provider.cc
index 5de9788..a795de8 100644
--- a/cc/raster/gpu_raster_buffer_provider.cc
+++ b/cc/raster/gpu_raster_buffer_provider.cc

@@ -398,7 +398,7 @@
                               base::bits::Log2Floor(sample_count), 0, 7, 7);
   // With Raw Draw, the framebuffer will be the rasterization target. It cannot
   // support LCD text, so disable LCD text for Raw Draw backings.
-  // TODO(penghuang): remove it when GrSlug can be serialized.
+  // TODO(penghuang): remove it when sktext::gpu::Slug can be serialized.
   bool is_raw_draw_backing =
       client_->is_using_raw_draw_ && !backing_->overlay_candidate;
   bool use_lcd_text = playback_settings.use_lcd_text && !is_raw_draw_backing;