Remove SkBitmapHeap and SkBitmapHeapReader. They're unused.

src/core/SkPictureData.h

Index: src/core/SkPictureData.h
diff --git a/src/core/SkPictureData.h b/src/core/SkPictureData.h
index 78ca25d4ca7ccf1673ba1f3a845481df03d8de18..ec147f7e2117e23b8567749d861a7fa0523564f0 100644
--- a/src/core/SkPictureData.h
+++ b/src/core/SkPictureData.h
@@ -153,10 +153,6 @@ private:
     bool parseBufferTag(SkReadBuffer&, uint32_t tag, uint32_t size);
     void flattenToBuffer(SkWriteBuffer&) const;
 
-    // Only used by getBitmap() if the passed in index is SkBitmapHeap::INVALID_SLOT. This empty
-    // bitmap allows playback to draw nothing and move on.
-    SkBitmap fBadBitmap;
-
     SkTArray<SkBitmap> fBitmaps;
     SkTArray<SkPaint>  fPaints;
     SkTArray<SkPath>   fPaths;