Revert of Revert[2] of add ImageShader, sharing code with its Bitmap cousin

src/image/SkImage_Raster.cpp

Index: src/image/SkImage_Raster.cpp
diff --git a/src/image/SkImage_Raster.cpp b/src/image/SkImage_Raster.cpp
index 64f875924e6796e4c8030a87bfaf4f7bca69f4b9..30ea7cc1a45a7937d979d0e6170d2febfa5e33e4 100644
--- a/src/image/SkImage_Raster.cpp
+++ b/src/image/SkImage_Raster.cpp
@@ -80,6 +80,10 @@
 
     SkPixelRef* getPixelRef() const { return fBitmap.pixelRef(); }
 
+    SkShader* onNewShader(SkShader::TileMode,
+                          SkShader::TileMode,
+                          const SkMatrix* localMatrix) const override;
+
     bool isOpaque() const override;
     bool onAsLegacyBitmap(SkBitmap*, LegacyBitmapMode) const override;
 
@@ -139,6 +143,11 @@
 }
 
 SkImage_Raster::~SkImage_Raster() {}
+
+SkShader* SkImage_Raster::onNewShader(SkShader::TileMode tileX, SkShader::TileMode tileY,
+                                      const SkMatrix* localMatrix) const {
+    return SkShader::CreateBitmapShader(fBitmap, tileX, tileY, localMatrix);
+}
 
 bool SkImage_Raster::onReadPixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRowBytes,
                                   int srcX, int srcY) const {