Implement the logic to kick off image decoding jobs for TileManager

cc/picture_pile_impl.cc

Index: cc/picture_pile_impl.cc
diff --git a/cc/picture_pile_impl.cc b/cc/picture_pile_impl.cc
index ff136e513840048698269c0df7aaa050138b31b1..05f9584ae58bb1f82306f7d244053b42a32909d1 100644
--- a/cc/picture_pile_impl.cc
+++ b/cc/picture_pile_impl.cc
@@ -79,4 +79,14 @@ void PicturePileImpl::Raster(
                                          rasterizeBeginTime).InSecondsF();
 }
 
+void PicturePileImpl::GatherPixelRefs(
+    const gfx::Rect& rect, std::list<skia::LazyPixelRef*>& pixel_refs) {
+  std::list<skia::LazyPixelRef*> result;
+  for (PicturePile::Pile::const_iterator i = pile_.begin();
+      i != pile_.end(); ++i) {
+    (*i)->GatherPixelRefs(rect, result);
+    pixel_refs.splice(pixel_refs.end(), result);
+  }
+}
+
 }  // namespace cc