Split GrDDL- & GrDirect- Contexts into their own files

Following up on an prior CLs TODO

Change-Id: I99397d4ffa5cc67b39726900f48b399e38fdbdd9
Reviewed-on: https://skia-review.googlesource.com/113201
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
diff --git a/gn/gpu.gni b/gn/gpu.gni
index 27a50a9..86e2a03 100644
--- a/gn/gpu.gni
+++ b/gn/gpu.gni
@@ -72,10 +72,12 @@
   "$_src/gpu/GrContext.cpp",
   "$_src/gpu/GrContextPriv.h",
   "$_src/gpu/GrCoordTransform.h",
+  "$_src/gpu/GrDDLContext.cpp",
   "$_src/gpu/GrDefaultGeoProcFactory.cpp",
   "$_src/gpu/GrDefaultGeoProcFactory.h",
   "$_src/gpu/GrDeferredProxyUploader.h",
   "$_src/gpu/GrDeferredUpload.h",
+  "$_src/gpu/GrDirectContext.cpp",
   "$_src/gpu/GrDistanceFieldGenFromVector.cpp",
   "$_src/gpu/GrDistanceFieldGenFromVector.h",
   "$_src/gpu/GrDrawingManager.cpp",