Convert readSurfacePixels to use a draw context instead of a texture

src/gpu/vk/GrVkGpu.cpp

Index: src/gpu/vk/GrVkGpu.cpp
diff --git a/src/gpu/vk/GrVkGpu.cpp b/src/gpu/vk/GrVkGpu.cpp
index e779bac99baec1fb5d8bb15f22f36ae6afba6b55..a09a805e3c998deaff015124c0041adb59109b70 100644
--- a/src/gpu/vk/GrVkGpu.cpp
+++ b/src/gpu/vk/GrVkGpu.cpp
@@ -1388,7 +1388,7 @@ bool GrVkGpu::onGetReadPixelsInfo(GrSurface* srcSurface, int width, int height,
     tempDrawInfo->fTempSurfaceDesc.fHeight = height;
     tempDrawInfo->fTempSurfaceDesc.fSampleCnt = 0;
     tempDrawInfo->fTempSurfaceDesc.fOrigin = kTopLeft_GrSurfaceOrigin; // no CPU y-flip for TL.
-    tempDrawInfo->fUseExactScratch = false;
+    tempDrawInfo->fTempSurfaceFit = SkBackingFit::kApprox;
 
     // For now assume no swizzling, we may change that below.
     tempDrawInfo->fSwizzle = GrSwizzle::RGBA();