Revert of cc: Shrink size of display item

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 3ce166222de618831ec6f8597ef73a31b7235c30..4d245383f40944554310348344d11640c8853bc6 100644
--- a/cc/playback/display_item_list.h
+++ b/cc/playback/display_item_list.h
@@ -22,8 +22,6 @@
 class SkPictureRecorder;
 
 namespace cc {
-class DisplayItem;
-class DrawingDisplayItem;
 
 namespace proto {
 class DisplayItemList;
@@ -62,23 +60,20 @@
   // is_suitable_for_gpu_rasterization_ and approximate_op_count_.
   void RasterIntoCanvas(const DisplayItem& display_item);
 
-  // Because processing happens in this function, all the set up for
-  // this item should be done via the args, which is why the return
-  // type needs to be const, to prevent set-after-processing mistakes.
-  template <typename DisplayItemType, typename... Args>
-  const DisplayItemType& CreateAndAppendItem(const gfx::Rect& visual_rect,
-                                             const Args&... args) {
+  template <typename DisplayItemType>
+  DisplayItemType* CreateAndAppendItem(const gfx::Rect& visual_rect) {
+#if DCHECK_IS_ON()
+    needs_process_ = true;
+#endif
     visual_rects_.push_back(visual_rect);
-    // TODO(enne): This should forward the args.
-    auto* item = &items_.AllocateAndConstruct<DisplayItemType>(args...);
-    approximate_op_count_ += item->ApproximateOpCount();
-    // TODO(crbug.com/513016): None of the items might individually trigger a
-    // veto even though they collectively have enough "bad" operations that a
-    // corresponding flattened Picture would get vetoed.
-    is_suitable_for_gpu_rasterization_ &= item->IsSuitableForGpuRasterization();
-    ProcessAppendedItem(item);
-    return *item;
+    ProcessAppendedItemsOnTheFly();
+    return &items_.AllocateAndConstruct<DisplayItemType>();
   }
+
+  // Removes the last item. This cannot be called on lists with cached pictures
+  // (since the data may already have been incorporated into cached picture
+  // sizes, etc).
+  void RemoveLast();
 
   // Called after all items are appended, to process the items and, if
   // applicable, create an internally cached SkPicture.
@@ -109,7 +104,16 @@
                   bool retain_individual_display_items);
   ~DisplayItemList();
 
-  void ProcessAppendedItem(const DisplayItem* item);
+  // While appending new items, if they are not being retained, this can process
+  // periodically to avoid retaining all the items and processing at the end.
+  void ProcessAppendedItemsOnTheFly();
+  void ProcessAppendedItems();
+#if DCHECK_IS_ON()
+  bool ProcessAppendedItemsCalled() const { return !needs_process_; }
+  bool needs_process_;
+#else
+  bool ProcessAppendedItemsCalled() const { return true; }
+#endif
 
   ContiguousContainer<DisplayItem> items_;
   // The visual rects associated with each of the display items in the
@@ -132,6 +136,9 @@
   // Memory usage due to the cached SkPicture.
   size_t picture_memory_usage_;
 
+  // Memory usage due to external data held by display items.
+  size_t external_memory_usage_;
+
   DiscardableImageMap image_map_;
 
   friend class base::RefCountedThreadSafe<DisplayItemList>;