remove all guards for changes to drawBitmapRect / drawImageRect

BUG=skia:

Review URL: https://codereview.chromium.org/1239193002
diff --git a/src/gpu/SkGpuDevice.h b/src/gpu/SkGpuDevice.h
index ec3bfbd..8d557bc 100644
--- a/src/gpu/SkGpuDevice.h
+++ b/src/gpu/SkGpuDevice.h
@@ -95,8 +95,7 @@
                             const SkMatrix&, const SkPaint&) override;
     virtual void drawBitmapRect(const SkDraw&, const SkBitmap&,
                                 const SkRect* srcOrNull, const SkRect& dst,
-                                const SkPaint& paint,
-                                SK_VIRTUAL_CONSTRAINT_TYPE) override;
+                                const SkPaint& paint, SkCanvas::SrcRectConstraint) override;
     virtual void drawSprite(const SkDraw&, const SkBitmap& bitmap,
                             int x, int y, const SkPaint& paint) override;
     virtual void drawText(const SkDraw&, const void* text, size_t len,