Convert readSurfacePixels to use a draw context instead of a texture
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2165523003

Review-Url: https://codereview.chromium.org/2165523003
diff --git a/src/gpu/vk/GrVkGpu.cpp b/src/gpu/vk/GrVkGpu.cpp
index e779bac..a09a805 100644
--- a/src/gpu/vk/GrVkGpu.cpp
+++ b/src/gpu/vk/GrVkGpu.cpp
@@ -1388,7 +1388,7 @@
     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();