Add drawDrawable support to GrRenderTargetContext.

This also includes adding drawable Op and plumbing it through to the GPU.

BUG=skia:

Change-Id: I0b2464c5a458c2fbf05b9528e47b9e6e3ac27d57
Reviewed-on: https://skia-review.googlesource.com/c/9645
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
diff --git a/gn/gpu.gni b/gn/gpu.gni
index c18acfe..3c33b26 100644
--- a/gn/gpu.gni
+++ b/gn/gpu.gni
@@ -249,10 +249,13 @@
   "$_src/gpu/ops/GrDashLinePathRenderer.h",
   "$_src/gpu/ops/GrDashOp.cpp",
   "$_src/gpu/ops/GrDashOp.h",
+  "$_src/gpu/ops/GrDebugMarkerOp.h",
   "$_src/gpu/ops/GrDefaultPathRenderer.cpp",
   "$_src/gpu/ops/GrDefaultPathRenderer.h",
   "$_src/gpu/ops/GrDebugMarkerOp.cpp",
   "$_src/gpu/ops/GrDebugMarkerOp.h",
+  "$_src/gpu/ops/GrDrawableOp.cpp",
+  "$_src/gpu/ops/GrDrawableOp.h",
   "$_src/gpu/ops/GrDrawAtlasOp.cpp",
   "$_src/gpu/ops/GrDrawAtlasOp.h",
   "$_src/gpu/ops/GrDrawOp.h",