Don't copy image buffer when calculating size.

src/image/SkImage_Base.h

Index: src/image/SkImage_Base.h
diff --git a/src/image/SkImage_Base.h b/src/image/SkImage_Base.h
index 7fbe97deac1901b1aba05c19eb6128137683d219..012120d4224ba721cea1a8e0dc0d03f8b63bd68c 100644
--- a/src/image/SkImage_Base.h
+++ b/src/image/SkImage_Base.h
@@ -46,6 +46,8 @@ public:
 
     virtual GrTexture* peekTexture() const { return nullptr; }
 #if SK_SUPPORT_GPU
+    virtual bool canGenerateTexture(const GrContextThreadSafeProxy& proxy) const { return false; }
+
     virtual sk_sp<GrTexture> refPinnedTexture(uint32_t* uniqueID) const { return nullptr; }
 #endif
     virtual SkImageCacherator* peekCacherator() const { return nullptr; }