Make SkImage::readYUV8Planes const

src/image/SkImage.cpp

Index: src/image/SkImage.cpp
diff --git a/src/image/SkImage.cpp b/src/image/SkImage.cpp
index 7507591ee5697bd79e34e9718c76a86f11755be4..e6ea9bd1212021e0397e2325691066797fc22490 100644
--- a/src/image/SkImage.cpp
+++ b/src/image/SkImage.cpp
@@ -265,7 +265,7 @@ bool SkImage::readPixels(const SkPixmap& pmap, int srcX, int srcY, CachingHint c
 #include "SkRGBAToYUV.h"
 
 bool SkImage::readYUV8Planes(const SkISize sizes[3], void* const planes[3],
-                             const size_t rowBytes[3], SkYUVColorSpace colorSpace) {
+                             const size_t rowBytes[3], SkYUVColorSpace colorSpace) const {
 #if SK_SUPPORT_GPU
     if (GrTexture* texture = as_IB(this)->peekTexture()) {
         if (GrTextureToYUVPlanes(texture, sizes, planes, rowBytes, colorSpace)) {