cc: Add ReverseSpiralDifferenceIterator.

cc/base/tiling_data_unittest.cc

 // Copyright 2013 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/base/tiling_data.h"
 
 #include <algorithm>
 #include <vector>
 
 #include "cc/test/geometry_test_utils.h"
@@ skipping 1356 matching lines @@
   TilingData data(gfx::Size(100, 100), gfx::Size(), false);
   TestDiff(data, gfx::Rect(100, 100), gfx::Rect(5, 5), 0);
 }
 
 void TestSpiralIterate(int source_line_number,
                        const TilingData& tiling_data,
                        const gfx::Rect& consider,
                        const gfx::Rect& ignore,
                        const gfx::Rect& center,
                        const std::vector<std::pair<int, int>>& expected) {
-  std::vector<std::pair<int, int>> actual;
+  std::vector<std::pair<int, int>> actual_forward;
   for (TilingData::SpiralDifferenceIterator it(
            &tiling_data, consider, ignore, center);
        it;
        ++it) {
-    actual.push_back(it.index());
+    actual_forward.push_back(it.index());
   }
 
-  EXPECT_EQ(expected.size(), actual.size()) << "error from line "
-                                            << source_line_number;
-  for (size_t i = 0; i < std::min(expected.size(), actual.size()); ++i) {
-    EXPECT_EQ(expected[i].first, actual[i].first)
+  EXPECT_EQ(expected.size(), actual_forward.size()) << "error from line "
+                                                    << source_line_number;
+  for (size_t i = 0; i < std::min(expected.size(), actual_forward.size());
+       ++i) {
+    EXPECT_EQ(expected[i].first, actual_forward[i].first)
         << "i: " << i << " error from line: " << source_line_number;
-    EXPECT_EQ(expected[i].second, actual[i].second)
+    EXPECT_EQ(expected[i].second, actual_forward[i].second)
+        << "i: " << i << " error from line: " << source_line_number;
+  }
+
+  std::vector<std::pair<int, int>> actual_reverse;
+  for (TilingData::ReverseSpiralDifferenceIterator it(
+           &tiling_data, consider, ignore, center);
+       it;
+       ++it) {
+    actual_reverse.push_back(it.index());
+  }
+
+  std::vector<std::pair<int, int>> reversed_expected = expected;
+  std::reverse(reversed_expected.begin(), reversed_expected.end());
+  EXPECT_EQ(reversed_expected.size(), actual_reverse.size())
+      << "error from line " << source_line_number;
+  for (size_t i = 0;
+       i < std::min(reversed_expected.size(), actual_reverse.size());
+       ++i) {
+    EXPECT_EQ(reversed_expected[i].first, actual_reverse[i].first)
+        << "i: " << i << " error from line: " << source_line_number;
+    EXPECT_EQ(reversed_expected[i].second, actual_reverse[i].second)
         << "i: " << i << " error from line: " << source_line_number;
   }
 }
 
 TEST(TilingDataTest, SpiralDifferenceIteratorNoIgnoreFullConsider) {
   TilingData tiling_data(gfx::Size(10, 10), gfx::Size(30, 30), false);
   gfx::Rect consider(30, 30);
   gfx::Rect ignore;
   std::vector<std::pair<int, int>> expected;
 
@@ skipping 530 matching lines @@
   expected.push_back(std::make_pair(2, 2));
   expected.push_back(std::make_pair(2, 1));
   expected.push_back(std::make_pair(2, 0));
 
   TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
 }
 
 }  // namespace
 
 }  // namespace cc