Partially defer SkImage_Gpu

One of SkImageCacherator, GrBitmapTextureMaker, GrImageTextureMaker, GrTextureAdjuster, GrTextureProducer or SkImage has to take the first step. This is probably the least odd of the options.

Change-Id: Ie167034553451f4b3633a5a1548dbd4d75839b3d
Reviewed-on: https://skia-review.googlesource.com/9488
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
diff --git a/include/private/GrSurfaceProxy.h b/include/private/GrSurfaceProxy.h
index dd06f32..31e0f1d 100644
--- a/include/private/GrSurfaceProxy.h
+++ b/include/private/GrSurfaceProxy.h
@@ -331,7 +331,8 @@
     // For wrapped resources, 'fDesc' will always be filled in from the wrapped resource.
     const GrSurfaceDesc  fDesc;
     const SkBackingFit   fFit;      // always exact for wrapped resources
-    const SkBudgeted     fBudgeted; // set from the backing resource for wrapped resources
+    mutable SkBudgeted   fBudgeted; // set from the backing resource for wrapped resources
+                                    // mutable bc of SkSurface/SkImage wishy-washiness
     const uint32_t       fFlags;
     const UniqueID       fUniqueID; // set from the backing resource for wrapped resources