diff --git a/tools/viewer/Slide.h b/tools/viewer/Slide.h
index 023cd6b..a2ee307 100644
--- a/tools/viewer/Slide.h
+++ b/tools/viewer/Slide.h
@@ -21,9 +21,7 @@
 public:
     virtual ~Slide() {}
 
-    virtual SkISize getDimensions() const {
-        return SkISize::Make(0, 0);
-    }
+    virtual SkISize getDimensions() const = 0;
 
     virtual void draw(SkCanvas* canvas) = 0;
     virtual bool animate(const SkAnimTimer&) { return false;  }