Fix height calculation when doing copyImageToBuffer

The bug only manifested when we were forcing copies from the origin.

Bug: skia:
Change-Id: I63f17ad9282b10f0d9c9c9ef38031faad32e20a3
Reviewed-on: https://skia-review.googlesource.com/110445
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>

src/gpu/vk/GrVkGpu.cpp

@@ -1982,8 +1982,9 @@ bool GrVkGpu::onReadPixels(GrSurface* surface, GrSurfaceOrigin origin, int left,
     }
 
     size_t transBufferRowBytes = bpp * region.imageExtent.width;
+    size_t imageRows = bpp * region.imageExtent.height;
     GrVkTransferBuffer* transferBuffer =
-            static_cast<GrVkTransferBuffer*>(this->createBuffer(transBufferRowBytes * height,
+            static_cast<GrVkTransferBuffer*>(this->createBuffer(transBufferRowBytes * imageRows,
                                                                 kXferGpuToCpu_GrBufferType,
                                                                 kStream_GrAccessPattern));