Allow filters to specify their initial visual rect.

cc/playback/display_item_list.h

Index: cc/playback/display_item_list.h
diff --git a/cc/playback/display_item_list.h b/cc/playback/display_item_list.h
index 2f19bb77f4eba89e0c7971e96129818bde790e92..83ad4f43de24ccac48a1f5624b3d794e3a1876fc 100644
--- a/cc/playback/display_item_list.h
+++ b/cc/playback/display_item_list.h
@@ -73,10 +73,24 @@ class CC_EXPORT DisplayItemList
   // Because processing happens in these CreateAndAppend functions, all the set
   // up for the item should be done via the args, which is why the return type
   // needs to be const, to prevent set-after-processing mistakes.
+
+  // Most paired begin item types default to an empty visual rect, which will
+  // subsequently be grown as needed to encompass any contained items that draw
+  // content, such as drawing or filter items.
   template <typename DisplayItemType, typename... Args>
   const DisplayItemType& CreateAndAppendPairedBeginItem(Args&&... args) {
+    return CreateAndAppendPairedBeginItemWithVisualRect<DisplayItemType>(
+        gfx::Rect(), std::forward<Args>(args)...);
+  }
+
+  // This method variant is exposed to allow filters to specify their visual
+  // rect since they may draw content despite containing no drawing items.
+  template <typename DisplayItemType, typename... Args>
+  const DisplayItemType& CreateAndAppendPairedBeginItemWithVisualRect(

[vmpstr, 2016/08/11 23:39:37]

It seems like we could just have CreateAndAppendPairedBeginItem always take a
visual rect and require clients to specify it even if it's empty. Why do you
prefer this approach?

[wkorman, 2016/08/12 00:17:08]

Yeah, I thought about that. There are ~41 callsites and in all but one case
they'd be passing an empty rect. And I also liked the idea of making it more
explicit via a separate method name.

If we could use a default arg I would have done that, but I think we can't due
to the following varargs.

In any case I'm fine with switching to one method and passing empty rect in the
41 callsites (only 14 are outside of tests) if you'd prefer.

+      const gfx::Rect& visual_rect,
+      Args&&... args) {
     size_t item_index = inputs_.visual_rects.size();
-    inputs_.visual_rects.push_back(gfx::Rect());
+    inputs_.visual_rects.push_back(visual_rect);
     inputs_.begin_item_indices.push_back(item_index);
 
     return AllocateAndConstruct<DisplayItemType>(std::forward<Args>(args)...);