cc: Clean up DisplayItemList API

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 710284e4c579c06173390638cf643dafada9c1ea..402e73f421f99678de974f9b5680d71c9afc2e44 100644
--- a/cc/playback/display_item_list.h
+++ b/cc/playback/display_item_list.h
@@ -76,8 +76,8 @@ class CC_EXPORT DisplayItemList
   template <typename DisplayItemType, typename... Args>
   const DisplayItemType& CreateAndAppendItem(const gfx::Rect& visual_rect,
                                              Args&&... args) {
-    visual_rects_.push_back(visual_rect);
-    auto* item = &items_.AllocateAndConstruct<DisplayItemType>(
+    inputs_.visual_rects.push_back(visual_rect);
+    auto* item = &inputs_.items.AllocateAndConstruct<DisplayItemType>(
         std::forward<Args>(args)...);
     approximate_op_count_ += item->ApproximateOpCount();
     ProcessAppendedItem(item);
@@ -89,7 +89,7 @@ class CC_EXPORT DisplayItemList
   void Finalize();
 
   void SetIsSuitableForGpuRasterization(bool is_suitable) {
-    is_suitable_for_gpu_rasterization_ = is_suitable;
+    inputs_.is_suitable_for_gpu_rasterization = is_suitable;
   }
   bool IsSuitableForGpuRasterization() const;
   int ApproximateOpCount() const;
@@ -108,14 +108,16 @@ class CC_EXPORT DisplayItemList
                                   float raster_scale,
                                   std::vector<DrawImage>* images);
 
-  gfx::Rect VisualRectForTesting(int index) { return visual_rects_[index]; }
+  gfx::Rect VisualRectForTesting(int index) {
+    return inputs_.visual_rects[index];
+  }
 
   ContiguousContainer<DisplayItem>::const_iterator begin() const {
-    return items_.begin();
+    return inputs_.items.begin();
   }
 
   ContiguousContainer<DisplayItem>::const_iterator end() const {
-    return items_.end();
+    return inputs_.items.end();
   }
 
  private:
@@ -126,21 +128,11 @@ class CC_EXPORT DisplayItemList
 
   void ProcessAppendedItem(const DisplayItem* item);
 
-  ContiguousContainer<DisplayItem> items_;
-  // The visual rects associated with each of the display items in the
-  // display item list. There is one rect per display item, and the
-  // position in |visual_rects_| matches the position of the item in
-  // |items_| . These rects are intentionally kept separate
-  // because they are not needed while walking the |items_| for raster.
-  std::vector<gfx::Rect> visual_rects_;
   sk_sp<SkPicture> picture_;
 
   std::unique_ptr<SkPictureRecorder> recorder_;
-  const DisplayItemListSettings settings_;
-  bool retain_individual_display_items_;
 
-  gfx::Rect layer_rect_;
-  bool is_suitable_for_gpu_rasterization_;
+  bool retain_individual_display_items_;
   int approximate_op_count_;
 
   // Memory usage due to the cached SkPicture.
@@ -148,6 +140,25 @@ class CC_EXPORT DisplayItemList
 
   DiscardableImageMap image_map_;
 
+  struct Inputs {
+    Inputs(gfx::Rect layer_rect, const DisplayItemListSettings& settings);
+    ~Inputs();
+
+    ContiguousContainer<DisplayItem> items;
+    // The visual rects associated with each of the display items in the
+    // display item list. There is one rect per display item, and the
+    // position in |visual_rects| matches the position of the item in
+    // |items| . These rects are intentionally kept separate
+    // because they are not needed while walking the |items| for raster.
+    std::vector<gfx::Rect> visual_rects;
+
+    const DisplayItemListSettings settings;
+    gfx::Rect layer_rect;
+    bool is_suitable_for_gpu_rasterization;
+  };
+
+  Inputs inputs_;
+
   friend class base::RefCountedThreadSafe<DisplayItemList>;
   FRIEND_TEST_ALL_PREFIXES(DisplayItemListTest, ApproximateMemoryUsage);
   DISALLOW_COPY_AND_ASSIGN(DisplayItemList);