cc: Use a ListContainer for DisplayItemList to reduce allocations.

cc/resources/largest_display_item.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cc/resources/largest_display_item.h"
+
+#include <algorithm>
+
+#include "cc/resources/clip_display_item.h"
+#include "cc/resources/clip_path_display_item.h"
+#include "cc/resources/compositing_display_item.h"
+#include "cc/resources/drawing_display_item.h"
+#include "cc/resources/filter_display_item.h"
+#include "cc/resources/float_clip_display_item.h"
+#include "cc/resources/transform_display_item.h"
+
+#include "third_party/skia/include/core/SkPicture.h"
+
+namespace {
+const size_t kLargestDisplayItemSize = sizeof(cc::TransformDisplayItem);
+}  // namespace
+
+namespace cc {
+
+size_t LargestDisplayItemSize() {
+  // Use compile assert to make sure largest is actually larger than all other
+  // type of display_items.
+  static_assert(sizeof(ClipDisplayItem) <= kLargestDisplayItemSize,
+                "Largest Draw Quad size needs update. ClipDisplayItem"
+                " is currently largest.");
+  static_assert(sizeof(EndClipDisplayItem) <= kLargestDisplayItemSize,
+                "Largest Draw Quad size needs update. EndClipDisplayItem"
+                " is currently largest.");
+  static_assert(sizeof(ClipPathDisplayItem) <= kLargestDisplayItemSize,
+                "Largest Draw Quad size needs update. ClipPathDisplayItem"
+                " is currently largest.");
+  static_assert(sizeof(EndClipPathDisplayItem) <= kLargestDisplayItemSize,
+                "Largest Draw Quad size needs update. EndClipPathDisplayItem"
+                " is currently largest.");
+  static_assert(sizeof(CompositingDisplayItem) <= kLargestDisplayItemSize,
+                "Largest Draw Quad size needs update. CompositingDisplayItem"
+                " is currently largest.");
+  static_assert(sizeof(EndCompositingDisplayItem) <= kLargestDisplayItemSize,
+                "Largest Draw Quad size needs update. EndCompositingDisplayItem"
+                " is currently largest.");
+  static_assert(sizeof(DrawingDisplayItem) <= kLargestDisplayItemSize,
+                "Largest Draw Quad size needs update. DrawingDisplayItem"
+                " is currently largest.");
+  static_assert(sizeof(FilterDisplayItem) <= kLargestDisplayItemSize,
+                "Largest Draw Quad size needs update. FilterDisplayItem"
+                " is currently largest.");
+  static_assert(sizeof(EndFilterDisplayItem) <= kLargestDisplayItemSize,
+                "Largest Draw Quad size needs update. EndFilterDisplayItem"
+                " is currently largest.");
+  static_assert(sizeof(FloatClipDisplayItem) <= kLargestDisplayItemSize,
+                "Largest Draw Quad size needs update. FloatClipDisplayItem"
+                " is currently largest.");
+  static_assert(sizeof(EndFloatClipDisplayItem) <= kLargestDisplayItemSize,
+                "Largest Draw Quad size needs update. EndFloatClipDisplayItem"
+                " is currently largest.");
+  static_assert(sizeof(TransformDisplayItem) <= kLargestDisplayItemSize,
+                "Largest Draw Quad size needs update. TransformDisplayItem"
+                " is currently largest.");
+  static_assert(sizeof(EndTransformDisplayItem) <= kLargestDisplayItemSize,
+                "Largest Draw Quad size needs update. EndTransformDisplayItem"
+                " is currently largest.");
+
+  return kLargestDisplayItemSize;
+}
+
+}  // namespace cc