remove dead methods now that we use specials exclusively for imagefilters

src/core/SkBitmapDevice.cpp

Index: src/core/SkBitmapDevice.cpp
diff --git a/src/core/SkBitmapDevice.cpp b/src/core/SkBitmapDevice.cpp
index 433bd66c621241987e12c2de8fa804f735b3cd62..36afe42f3ac220cf2fda3a6bdb2c472df3fe5939 100644
--- a/src/core/SkBitmapDevice.cpp
+++ b/src/core/SkBitmapDevice.cpp
@@ -364,6 +364,7 @@ void SkBitmapDevice::drawVertices(const SkDraw& draw, SkCanvas::VertexMode vmode
 
 void SkBitmapDevice::drawDevice(const SkDraw& draw, SkBaseDevice* device,
                                 int x, int y, const SkPaint& paint) {
+    SkASSERT(!paint.getImageFilter());
     draw.drawSprite(static_cast<SkBitmapDevice*>(device)->fBitmap, x, y, paint);
 }