GPU: always use TopLeft origin for saveLayer render targets.

Should have no user-visible result.

Change-Id: Iae444888557347bfdf75e6353966cde907ee0a1e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/222506
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Stephen White <senorblanco@chromium.org>

src/gpu/SkGpuDevice.cpp

@@ -1695,7 +1695,7 @@ SkBaseDevice* SkGpuDevice::onCreateDevice(const CreateInfo& cinfo, const SkPaint
             format, fit, cinfo.fInfo.width(), cinfo.fInfo.height(), config,
             fRenderTargetContext->colorSpaceInfo().refColorSpace(),
             fRenderTargetContext->numStencilSamples(), GrMipMapped::kNo,
-            kBottomLeft_GrSurfaceOrigin, &props));
+            kTopLeft_GrSurfaceOrigin, &props));
     if (!rtc) {
         return nullptr;
     }