add support for clears to Metal backend

Bug: skia:
Change-Id: I35d9fcf096d078d6dc04093e3591df0ac12079b7
Reviewed-on: https://skia-review.googlesource.com/c/161821
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
diff --git a/src/gpu/GrRenderTargetOpList.cpp b/src/gpu/GrRenderTargetOpList.cpp
index 8215df7..41f4a67 100644
--- a/src/gpu/GrRenderTargetOpList.cpp
+++ b/src/gpu/GrRenderTargetOpList.cpp
@@ -118,6 +118,7 @@
 static GrGpuRTCommandBuffer* create_command_buffer(GrGpu* gpu,
                                                    GrRenderTarget* rt,
                                                    GrSurfaceOrigin origin,
+                                                   const SkRect& bounds,
                                                    GrLoadOp colorLoadOp,
                                                    GrColor loadClearColor,
                                                    GrLoadOp stencilLoadOp) {
@@ -137,7 +138,7 @@
         GrStoreOp::kStore,
     };
 
-    return gpu->getCommandBuffer(rt, origin, kColorLoadStoreInfo, stencilLoadAndStoreInfo);
+    return gpu->getCommandBuffer(rt, origin, bounds, kColorLoadStoreInfo, stencilLoadAndStoreInfo);
 }
 
 // TODO: this is where GrOp::renderTarget is used (which is fine since it
@@ -164,6 +165,7 @@
                                                     flushState->gpu(),
                                                     fTarget.get()->peekRenderTarget(),
                                                     fTarget.get()->origin(),
+                                                    fTarget.get()->getBoundsRect(),
                                                     fColorLoadOp,
                                                     fLoadClearColor,
                                                     fStencilLoadOp);