remove/deprecate SkBitmap::getTexture, as it now always returns false

src/core/SkSpecialImage.cpp

Index: src/core/SkSpecialImage.cpp
diff --git a/src/core/SkSpecialImage.cpp b/src/core/SkSpecialImage.cpp
index d01e485e831405e412c3597819a02e0c6dd9772e..fa7cbc6f6e112d9f44122c7a681ffdf1a27cb98e 100644
--- a/src/core/SkSpecialImage.cpp
+++ b/src/core/SkSpecialImage.cpp
@@ -290,7 +290,6 @@ private:
 sk_sp<SkSpecialImage> SkSpecialImage::MakeFromRaster(const SkIRect& subset,
                                                      const SkBitmap& bm,
                                                      const SkSurfaceProps* props) {
-    SkASSERT(nullptr == bm.getTexture());
     SkASSERT(rect_fits(subset, bm.width(), bm.height()));
 
     const SkBitmap* srcBM = &bm;