Reland "Initial definition of fill rect op"

This reverts commit 1a2476d2945654e40861292f778090fa04b3c267.

Reason for revert: Fixes printf signatures and asserts.

Original change's description:
> Revert "Initial definition of fill rect op"
> 
> This reverts commit d3c92d9a368be2d1f592bef4e65727721fc3ecf8.
> 
> Reason for revert: printf build failure on gcc, assert failures on CQ
> 
> Original change's description:
> > Initial definition of fill rect op
> > 
> > Bug: skia:
> > Change-Id: Ie0c99eb5163501853d1adc885bd3841f90a71924
> > Reviewed-on: https://skia-review.googlesource.com/c/163486
> > Reviewed-by: Brian Salomon <bsalomon@google.com>
> > Commit-Queue: Michael Ludwig <michaelludwig@google.com>
> 
> TBR=bsalomon@google.com,csmartdalton@google.com,michaelludwig@google.com
> 
> Change-Id: Ib32f91a39d91aeb87982a7b19719485e4a1bf8ae
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: skia:
> Reviewed-on: https://skia-review.googlesource.com/c/173233
> Reviewed-by: Michael Ludwig <michaelludwig@google.com>
> Commit-Queue: Michael Ludwig <michaelludwig@google.com>

TBR=bsalomon@google.com,csmartdalton@google.com,michaelludwig@google.com

Change-Id: I415913a269ba5bcdebd169b5ebc3510673247bfd
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/c/173234
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
diff --git a/gn/gpu.gni b/gn/gpu.gni
index 651fd16..a8a5bb16 100644
--- a/gn/gpu.gni
+++ b/gn/gpu.gni
@@ -262,6 +262,8 @@
   "$_src/gpu/ops/GrDrawOp.h",
   "$_src/gpu/ops/GrDrawVerticesOp.cpp",
   "$_src/gpu/ops/GrDrawVerticesOp.h",
+  "$_src/gpu/ops/GrFillRectOp.cpp",
+  "$_src/gpu/ops/GrFillRectOp.h",
   "$_src/gpu/ops/GrMeshDrawOp.cpp",
   "$_src/gpu/ops/GrMeshDrawOp.h",
   "$_src/gpu/ops/GrNonAAFillRectOp.cpp",