cc: Change RTree::Search to return results, add comments, more tests.

cc/paint/discardable_image_map_unittest.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/paint/discardable_image_map.h"
 
 #include <stddef.h>
 
 #include <memory>
 
@@ skipping 48 matching lines @@
   std::vector<PositionScaleDrawImage> GetDiscardableImagesInRect(
       const DiscardableImageMap& image_map,
       const gfx::Rect& rect) {
     std::vector<DrawImage> draw_images;
     // Choose a not-SRGB-and-not-invalid target color space to verify that it
     // is passed correctly to the resulting DrawImages.
     gfx::ColorSpace target_color_space = gfx::ColorSpace::CreateXYZD50();
     image_map.GetDiscardableImagesInRect(rect, 1.f, target_color_space,
                                          &draw_images);
 
-    std::vector<size_t> indices;
-    image_map.images_rtree_.Search(rect, &indices);
     std::vector<PositionScaleDrawImage> position_draw_images;
-    for (size_t index : indices) {
+    for (size_t index : image_map.images_rtree_.Search(rect)) {
       position_draw_images.push_back(
           PositionScaleDrawImage(image_map.all_images_[index].first.image(),
                                  image_map.all_images_[index].second,
                                  image_map.all_images_[index].first.scale()));
     }
 
     EXPECT_EQ(draw_images.size(), position_draw_images.size());
     for (size_t i = 0; i < draw_images.size(); ++i) {
       EXPECT_TRUE(draw_images[i].image() == position_draw_images[i].image);
       EXPECT_EQ(draw_images[i].target_color_space(), target_color_space);
@@ skipping 629 matching lines @@
   EXPECT_TRUE(discardable_image == images[0].image());
 
   images.clear();
   image_map_.GetDiscardableImagesInRect(gfx::Rect(105, 105, 5, 95), 1.f,
                                         target_color_space, &images);
   EXPECT_EQ(1u, images.size());
   EXPECT_TRUE(discardable_image2 == images[0].image());
 }
 
 }  // namespace cc