cc: Implement tile iteration order based on pyramid sequence. [old]

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 <stddef.h>
 
 #include <algorithm>
 #include <vector>
@@ skipping 1404 matching lines @@
   gfx::Rect consider(30, 30);
   gfx::Rect ignore;
   std::vector<std::pair<int, int>> expected;
 
   // Center is in the center of the tiling.
   gfx::Rect center(15, 15, 1, 1);
 
   // Layout of the tiling data, and expected return order:
   //   x 0 1 2
   //  y.------
-  //  0| 4 3 2
-  //  1| 5 * 1
-  //  2| 6 7 8
+  //  0| 7 5 3
+  //  1| 8 * 1
+  //  2| 6 4 2
   expected.push_back(std::make_pair(2, 1));
+  expected.push_back(std::make_pair(2, 2));
   expected.push_back(std::make_pair(2, 0));
+  expected.push_back(std::make_pair(1, 2));
   expected.push_back(std::make_pair(1, 0));
+  expected.push_back(std::make_pair(0, 2));
   expected.push_back(std::make_pair(0, 0));
   expected.push_back(std::make_pair(0, 1));
-  expected.push_back(std::make_pair(0, 2));
-  expected.push_back(std::make_pair(1, 2));
-  expected.push_back(std::make_pair(2, 2));
 
   TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
 
   // Center is off to the right side of the tiling (and far away).
   center = gfx::Rect(100, 15, 1, 1);
 
   // Layout of the tiling data, and expected return order:
   //   x 0 1 2
   //  y.------
   //  0| 7 4 1
-  //  1| 8 5 2 *
+  //  1| 8 5 2           *
   //  2| 9 6 3
   expected.clear();
   expected.push_back(std::make_pair(2, 0));
   expected.push_back(std::make_pair(2, 1));
   expected.push_back(std::make_pair(2, 2));
   expected.push_back(std::make_pair(1, 0));
   expected.push_back(std::make_pair(1, 1));
   expected.push_back(std::make_pair(1, 2));
   expected.push_back(std::make_pair(0, 0));
   expected.push_back(std::make_pair(0, 1));
@@ skipping 21 matching lines @@
   expected.push_back(std::make_pair(0, 2));
 
   TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
 
   // Center is off the top left side of the tiling.
   center = gfx::Rect(-60, -50, 1, 1);
 
   // Layout of the tiling data, and expected return order:
   // * x 0 1 2
   //  y.------
-  //  0| 1 2 6
-  //  1| 3 4 5
-  //  2| 7 8 9
+  //  0| 1 4 9
+  //  1| 2 3 8
+  //  2| 6 5 7
   expected.clear();
   expected.push_back(std::make_pair(0, 0));
-  expected.push_back(std::make_pair(1, 0));
   expected.push_back(std::make_pair(0, 1));
   expected.push_back(std::make_pair(1, 1));
+  expected.push_back(std::make_pair(1, 0));
+  expected.push_back(std::make_pair(1, 2));
+  expected.push_back(std::make_pair(0, 2));
+  expected.push_back(std::make_pair(2, 2));
   expected.push_back(std::make_pair(2, 1));
   expected.push_back(std::make_pair(2, 0));
-  expected.push_back(std::make_pair(0, 2));
-  expected.push_back(std::make_pair(1, 2));
-  expected.push_back(std::make_pair(2, 2));
 
   TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
 
   // Two tile center.
   center = gfx::Rect(15, 15, 1, 10);
 
   // Layout of the tiling data, and expected return order:
   //   x 0 1 2
   //  y.------
   //  0| 5 4 3
@@ skipping 34 matching lines @@
 
   // Consider is bottom right corner.
   consider = gfx::Rect(25, 25, 10, 10);
 
   // Layout of the tiling data, and expected return order:
   //   x 0 1 2 3 4
   //  y.----------
   //  0|
   //  1|   *
   //  2|     1 2
-  //  3|     3 4
+  //  3|     4 3
   //  4|
   expected.clear();
   expected.push_back(std::make_pair(2, 2));
   expected.push_back(std::make_pair(3, 2));
+  expected.push_back(std::make_pair(3, 3));
   expected.push_back(std::make_pair(2, 3));
-  expected.push_back(std::make_pair(3, 3));
 
   TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
 
   // Consider is one column.
   consider = gfx::Rect(11, 0, 1, 100);
 
   // Layout of the tiling data, and expected return order:
   //   x 0 1 2 3 4
   //  y.----------
   //  0|   2
   //  1|   *
-  //  2|   3
-  //  3|   4
-  //  4|   5
+  //  2|   1
+  //  3|   3
+  //  4|   4
   expected.clear();
+  expected.push_back(std::make_pair(1, 2));
   expected.push_back(std::make_pair(1, 0));
-  expected.push_back(std::make_pair(1, 2));
   expected.push_back(std::make_pair(1, 3));
   expected.push_back(std::make_pair(1, 4));
 
   TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
 }
 
 TEST(TilingDataTest, SpiralDifferenceIteratorHasIgnore) {
   TilingData tiling_data(gfx::Size(10, 10), gfx::Size(50, 50), false);
   gfx::Rect consider(50, 50);
   std::vector<std::pair<int, int>> expected;
   gfx::Rect center(15, 15, 1, 1);
 
   // Full ignore.
   gfx::Rect ignore(50, 50);
 
   // Layout of the tiling data, and expected return order:
-  //   x 0 1 2 3 4
-  //  y.----------
-  //  0| . . . . .
-  //  1| . * . . .
-  //  2| . . . . .
-  //  3| . . . . .
-  //  4| . . . . .
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0|  I  I  I  I  I
+  //  1|  I  *  I  I  I
+  //  2|  I  I  I  I  I
+  //  3|  I  I  I  I  I
+  //  4|  I  I  I  I  I
   expected.clear();
 
   TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
 
   // 3 column ignore.
   ignore = gfx::Rect(15, 0, 20, 100);
 
   // Layout of the tiling data, and expected return order:
-  //   x 0 1 2 3 4
-  //  y.----------
-  //  0| 1 . . . 8
-  //  1| 2 * . . 7
-  //  2| 3 . . . 6
-  //  3| 4 . . . 5
-  //  4| 9 . . . 10
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0|  2  I  I  I  8
+  //  1|  3  *  I  I  7
+  //  2|  1  I  I  I  6
+  //  3|  4  I  I  I  5
+  //  4| 10  I  I  I  9
   expected.clear();
 
+  expected.push_back(std::make_pair(0, 2));
   expected.push_back(std::make_pair(0, 0));
   expected.push_back(std::make_pair(0, 1));
-  expected.push_back(std::make_pair(0, 2));
   expected.push_back(std::make_pair(0, 3));
   expected.push_back(std::make_pair(4, 3));
   expected.push_back(std::make_pair(4, 2));
   expected.push_back(std::make_pair(4, 1));
   expected.push_back(std::make_pair(4, 0));
+  expected.push_back(std::make_pair(4, 4));
   expected.push_back(std::make_pair(0, 4));
-  expected.push_back(std::make_pair(4, 4));
 
   TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
 
   // Ignore covers the top half.
   ignore = gfx::Rect(50, 25);
 
   // Layout of the tiling data, and expected return order:
-  //   x 0 1 2 3 4
-  //  y.----------
-  //  0| . . . . .
-  //  1| . * . . .
-  //  2| . . . . .
-  //  3| 1 2 3 4 5
-  //  4| 6 7 8 9 10
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0|  I  I  I  I  I
+  //  1|  I  *  I  I  I
+  //  2|  I  I  I  I  I
+  //  3|  2  3  4  1  5
+  //  4|  7  8  9 10  6
   expected.clear();
 
+  expected.push_back(std::make_pair(3, 3));
   expected.push_back(std::make_pair(0, 3));
   expected.push_back(std::make_pair(1, 3));
   expected.push_back(std::make_pair(2, 3));
-  expected.push_back(std::make_pair(3, 3));
   expected.push_back(std::make_pair(4, 3));
+  expected.push_back(std::make_pair(4, 4));
   expected.push_back(std::make_pair(0, 4));
   expected.push_back(std::make_pair(1, 4));
   expected.push_back(std::make_pair(2, 4));
   expected.push_back(std::make_pair(3, 4));
-  expected.push_back(std::make_pair(4, 4));
 
   TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
 }
 
 TEST(TilingDataTest, SpiralDifferenceIteratorRectangleCenter) {
   TilingData tiling_data(gfx::Size(10, 10), gfx::Size(50, 50), false);
   gfx::Rect consider(50, 50);
   std::vector<std::pair<int, int>> expected;
   gfx::Rect ignore;
 
   // Two cell center
   gfx::Rect center(25, 25, 1, 10);
 
   // Layout of the tiling data, and expected return order:
-  //   x 0 1 2 3 4
-  //  y.----------
-  //  0| J I H G F
-  //  1| K 5 4 3 E
-  //  2| L 6 * 2 D
-  //  3| M 7 * 1 C
-  //  4| N 8 9 A B
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0| 19 18 17 16 15
+  //  1| 20  8  6  4 14
+  //  2| 21  9  *  2 13
+  //  3| 22 10  *  1 12
+  //  4| 23  7  5  3 11
   expected.clear();
 
   expected.push_back(std::make_pair(3, 3));
   expected.push_back(std::make_pair(3, 2));
+  expected.push_back(std::make_pair(3, 4));
   expected.push_back(std::make_pair(3, 1));
+  expected.push_back(std::make_pair(2, 4));
   expected.push_back(std::make_pair(2, 1));
+  expected.push_back(std::make_pair(1, 4));
   expected.push_back(std::make_pair(1, 1));
   expected.push_back(std::make_pair(1, 2));
   expected.push_back(std::make_pair(1, 3));
-  expected.push_back(std::make_pair(1, 4));
-  expected.push_back(std::make_pair(2, 4));
-  expected.push_back(std::make_pair(3, 4));
   expected.push_back(std::make_pair(4, 4));
   expected.push_back(std::make_pair(4, 3));
   expected.push_back(std::make_pair(4, 2));
   expected.push_back(std::make_pair(4, 1));
   expected.push_back(std::make_pair(4, 0));
   expected.push_back(std::make_pair(3, 0));
   expected.push_back(std::make_pair(2, 0));
   expected.push_back(std::make_pair(1, 0));
   expected.push_back(std::make_pair(0, 0));
   expected.push_back(std::make_pair(0, 1));
   expected.push_back(std::make_pair(0, 2));
   expected.push_back(std::make_pair(0, 3));
   expected.push_back(std::make_pair(0, 4));
 
   TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
 
   // Three by two center.
   center = gfx::Rect(15, 25, 20, 10);
 
   // Layout of the tiling data, and expected return order:
-  //   x 0 1 2 3 4
-  //  y.----------
-  //  0| J I H G F
-  //  1| 7 6 5 4 3
-  //  2| 8 * * * 2
-  //  3| 9 * * * 1
-  //  4| A B C D E
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0| 19 18 17 16 15
+  //  1| 12 10  9  8  4
+  //  2| 13  *  *  *  2
+  //  3| 14  *  *  *  1
+  //  4| 11  5  6  7  3
   expected.clear();
 
   expected.push_back(std::make_pair(4, 3));
   expected.push_back(std::make_pair(4, 2));
+  expected.push_back(std::make_pair(4, 4));
   expected.push_back(std::make_pair(4, 1));
+  expected.push_back(std::make_pair(1, 4));
+  expected.push_back(std::make_pair(2, 4));
+  expected.push_back(std::make_pair(3, 4));
   expected.push_back(std::make_pair(3, 1));
   expected.push_back(std::make_pair(2, 1));
   expected.push_back(std::make_pair(1, 1));
+  expected.push_back(std::make_pair(0, 4));
   expected.push_back(std::make_pair(0, 1));
   expected.push_back(std::make_pair(0, 2));
   expected.push_back(std::make_pair(0, 3));
-  expected.push_back(std::make_pair(0, 4));
-  expected.push_back(std::make_pair(1, 4));
-  expected.push_back(std::make_pair(2, 4));
-  expected.push_back(std::make_pair(3, 4));
-  expected.push_back(std::make_pair(4, 4));
   expected.push_back(std::make_pair(4, 0));
   expected.push_back(std::make_pair(3, 0));
   expected.push_back(std::make_pair(2, 0));
   expected.push_back(std::make_pair(1, 0));
   expected.push_back(std::make_pair(0, 0));
 
   TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
 
   // Column center off the left side.
   center = gfx::Rect(-50, 0, 30, 50);
 
   // Layout of the tiling data, and expected return order:
-  //    x 0 1 2 3 4
-  //   y.----------
-  // * 0| 5 A F K P
-  // * 1| 4 9 E J O
-  // * 2| 3 8 D I N
-  // * 3| 2 7 C H M
-  // * 4| 1 6 B G L
+  //    x  0  1  2  3  4
+  //   y.---------------
+  // * 0|  5 10 15 20 25
+  // * 1|  4  9 14 19 24
+  // * 2|  3  8 13 18 23
+  // * 3|  2  7 12 17 22
+  // * 4|  1  6 11 16 21
   expected.clear();
 
   expected.push_back(std::make_pair(0, 4));
   expected.push_back(std::make_pair(0, 3));
   expected.push_back(std::make_pair(0, 2));
   expected.push_back(std::make_pair(0, 1));
   expected.push_back(std::make_pair(0, 0));
   expected.push_back(std::make_pair(1, 4));
   expected.push_back(std::make_pair(1, 3));
   expected.push_back(std::make_pair(1, 2));
@@ skipping 26 matching lines @@
   gfx::Rect ignore;
 
   // Ignore contains, but is not equal to, consider and center.
   ignore = gfx::Rect(15, 0, 20, 30);
   consider = gfx::Rect(20, 10, 10, 20);
   center = gfx::Rect(25, 0, 5, 5);
 
   // Layout of the tiling data, and expected return order:
   //   x 0 1 2
   //  y.------
-  //  0|   . *
-  //  1|   . .
-  //  2|   . .
+  //  0|   I *
+  //  1|   I I
+  //  2|   I I
   expected.clear();
 
   TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
 
   // Center intersects with consider.
   ignore = gfx::Rect();
   center = gfx::Rect(0, 15, 30, 15);
   consider = gfx::Rect(15, 30);
 
   // Layout of the tiling data, and expected return order:
@@ skipping 10 matching lines @@
   TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
 
   // Consider and ignore are non-intersecting.
   ignore = gfx::Rect(5, 30);
   consider = gfx::Rect(25, 0, 5, 30);
   center = gfx::Rect(15, 0, 1, 1);
 
   // Layout of the tiling data, and expected return order:
   //   x 0 1 2
   //  y.------
-  //  0| . * 1
-  //  1| .   2
-  //  2| .   3
+  //  0| I * 1
+  //  1| I   2
+  //  2| I   3
   expected.clear();
 
   expected.push_back(std::make_pair(2, 0));
   expected.push_back(std::make_pair(2, 1));
   expected.push_back(std::make_pair(2, 2));
 
   TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
 
   // Center intersects with ignore.
   consider = gfx::Rect(30, 30);
   center = gfx::Rect(15, 0, 1, 30);
   ignore = gfx::Rect(0, 15, 30, 1);
 
   // Layout of the tiling data, and expected return order:
   //   x 0 1 2
   //  y.------
   //  0| 3 * 2
-  //  1| . * .
+  //  1| I * I
   //  2| 4 * 1
   expected.clear();
 
   expected.push_back(std::make_pair(2, 2));
   expected.push_back(std::make_pair(2, 0));
   expected.push_back(std::make_pair(0, 0));
   expected.push_back(std::make_pair(0, 2));
 
   TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
 
@@ skipping 36 matching lines @@
   // Empty center. Note: This arbitrarily puts the center to be off the top-left
   // corner.
   consider = gfx::Rect(30, 30);
   ignore = gfx::Rect();
   center = gfx::Rect();
 
   // Layout of the tiling data, and expected return order:
   // * x 0 1 2
   //  y.------
   //  0| 1 2 6
-  //  1| 3 4 5
-  //  2| 7 8 9
+  //  1| 4 3 5
+  //  2| 8 9 7
   expected.clear();
 
   expected.push_back(std::make_pair(0, 0));
   expected.push_back(std::make_pair(1, 0));
+  expected.push_back(std::make_pair(1, 1));
   expected.push_back(std::make_pair(0, 1));
-  expected.push_back(std::make_pair(1, 1));
   expected.push_back(std::make_pair(2, 1));
   expected.push_back(std::make_pair(2, 0));
+  expected.push_back(std::make_pair(2, 2));
   expected.push_back(std::make_pair(0, 2));
   expected.push_back(std::make_pair(1, 2));
-  expected.push_back(std::make_pair(2, 2));
 
   TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
 
   // Every rect is empty.
   ignore = gfx::Rect();
   center = gfx::Rect();
   consider = gfx::Rect();
 
   expected.clear();
   TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
 
   // Center is just to the left of cover, and off of the tiling's left side.
   consider = gfx::Rect(30, 30);
   ignore = gfx::Rect();
   center = gfx::Rect(-20, 0, 19, 30);
 
   // Layout of the tiling data, and expected return order:
-  //   x 0 1 2
-  //  y.------
-  // *0| 3 6 9
-  // *1| 2 5 8
-  // *2| 1 4 7
+  //    x 0 1 2
+  //   y.------
+  // * 0| 3 6 9
+  // * 1| 2 5 8
+  // * 2| 1 4 7
   expected.clear();
 
   expected.push_back(std::make_pair(0, 2));
   expected.push_back(std::make_pair(0, 1));
   expected.push_back(std::make_pair(0, 0));
   expected.push_back(std::make_pair(1, 2));
   expected.push_back(std::make_pair(1, 1));
   expected.push_back(std::make_pair(1, 0));
   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);
 }
 
+TEST(TilingDataTest, SpiralDifferenceIteratorWideTilesNoIgnoreFullConsider) {
+  TilingData tiling_data(gfx::Size(20, 10), gfx::Size(100, 50), false);
+  gfx::Rect consider(100, 50);
+  gfx::Rect ignore;
+  std::vector<std::pair<int, int>> expected;
+
+  // Center is in the center of the tiling.
+  gfx::Rect center(50, 25, 1, 1);
+
+  // Layout of the tiling data, and expected return order:
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0| 21 14 13 12 19
+  //  1| 22  7  5  3 17
+  //  2| 23  8  *  1 16
+  //  3| 24  6  4  2 15
+  //  4| 20  9 10 11 18
+  expected.push_back(std::make_pair(3, 2));
+  expected.push_back(std::make_pair(3, 3));
+  expected.push_back(std::make_pair(3, 1));
+  expected.push_back(std::make_pair(2, 3));
+  expected.push_back(std::make_pair(2, 1));
+  expected.push_back(std::make_pair(1, 3));
+  expected.push_back(std::make_pair(1, 1));
+  expected.push_back(std::make_pair(1, 2));
+  expected.push_back(std::make_pair(1, 4));
+  expected.push_back(std::make_pair(2, 4));
+  expected.push_back(std::make_pair(3, 4));
+  expected.push_back(std::make_pair(3, 0));
+  expected.push_back(std::make_pair(2, 0));
+  expected.push_back(std::make_pair(1, 0));
+  expected.push_back(std::make_pair(4, 3));
+  expected.push_back(std::make_pair(4, 2));
+  expected.push_back(std::make_pair(4, 1));
+  expected.push_back(std::make_pair(4, 4));
+  expected.push_back(std::make_pair(4, 0));
+  expected.push_back(std::make_pair(0, 4));
+  expected.push_back(std::make_pair(0, 0));
+  expected.push_back(std::make_pair(0, 1));
+  expected.push_back(std::make_pair(0, 2));
+  expected.push_back(std::make_pair(0, 3));
+
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+
+  // Center is off to the right side of the tiling (and far away).
+  center = gfx::Rect(200, 25, 1, 1);
+
+  // Layout of the tiling data, and expected return order:
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0| 21 16 11  6  1
+  //  1| 22 17 12  7  2
+  //  2| 23 18 13  8  3              *
+  //  3| 24 19 14  9  4
+  //  4| 25 20 15 10  5
+  expected.clear();
+  expected.push_back(std::make_pair(4, 0));
+  expected.push_back(std::make_pair(4, 1));
+  expected.push_back(std::make_pair(4, 2));
+  expected.push_back(std::make_pair(4, 3));
+  expected.push_back(std::make_pair(4, 4));
+  expected.push_back(std::make_pair(3, 0));
+  expected.push_back(std::make_pair(3, 1));
+  expected.push_back(std::make_pair(3, 2));
+  expected.push_back(std::make_pair(3, 3));
+  expected.push_back(std::make_pair(3, 4));
+  expected.push_back(std::make_pair(2, 0));
+  expected.push_back(std::make_pair(2, 1));
+  expected.push_back(std::make_pair(2, 2));
+  expected.push_back(std::make_pair(2, 3));
+  expected.push_back(std::make_pair(2, 4));
+  expected.push_back(std::make_pair(1, 0));
+  expected.push_back(std::make_pair(1, 1));
+  expected.push_back(std::make_pair(1, 2));
+  expected.push_back(std::make_pair(1, 3));
+  expected.push_back(std::make_pair(1, 4));
+  expected.push_back(std::make_pair(0, 0));
+  expected.push_back(std::make_pair(0, 1));
+  expected.push_back(std::make_pair(0, 2));
+  expected.push_back(std::make_pair(0, 3));
+  expected.push_back(std::make_pair(0, 4));
+
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+
+  // Center is the bottom right corner of the tiling.
+  center = gfx::Rect(90, 45, 1, 1);
+
+  // Layout of the tiling data, and expected return order:
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0| 20 15 14 13 12
+  //  1| 21 16  8  7  6
+  //  2| 22 17  9  5  4
+  //  3| 23 18 10  2  1
+  //  4| 24 19 11  3  *
+  expected.clear();
+  expected.push_back(std::make_pair(4, 3));
+  expected.push_back(std::make_pair(3, 3));
+  expected.push_back(std::make_pair(3, 4));
+  expected.push_back(std::make_pair(4, 2));
+  expected.push_back(std::make_pair(3, 2));
+  expected.push_back(std::make_pair(4, 1));
+  expected.push_back(std::make_pair(3, 1));
+  expected.push_back(std::make_pair(2, 1));
+  expected.push_back(std::make_pair(2, 2));
+  expected.push_back(std::make_pair(2, 3));
+  expected.push_back(std::make_pair(2, 4));
+  expected.push_back(std::make_pair(4, 0));
+  expected.push_back(std::make_pair(3, 0));
+  expected.push_back(std::make_pair(2, 0));
+  expected.push_back(std::make_pair(1, 0));
+  expected.push_back(std::make_pair(1, 1));
+  expected.push_back(std::make_pair(1, 2));
+  expected.push_back(std::make_pair(1, 3));
+  expected.push_back(std::make_pair(1, 4));
+  expected.push_back(std::make_pair(0, 0));
+  expected.push_back(std::make_pair(0, 1));
+  expected.push_back(std::make_pair(0, 2));
+  expected.push_back(std::make_pair(0, 3));
+  expected.push_back(std::make_pair(0, 4));
+
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+
+  // Center is off the top left side of the tiling.
+  center = gfx::Rect(-60, -50, 1, 1);
+
+  // Layout of the tiling data, and expected return order:
+  // Layout of the tiling data, and expected return order:
+  //  *
+  //
+  //
+  //
+  //
+  //            x  0  1  2  3  4
+  //           y.---------------
+  //           0|  1  2 20 21 24
+  //           1|  3  4  5 22 23
+  //           2|  6  7  8  9 25
+  //           3| 10 11 12 13 14
+  //           4| 15 16 17 18 19
+  expected.clear();
+  expected.push_back(std::make_pair(0, 0));
+  expected.push_back(std::make_pair(1, 0));
+  expected.push_back(std::make_pair(0, 1));
+  expected.push_back(std::make_pair(1, 1));
+  expected.push_back(std::make_pair(2, 1));
+  expected.push_back(std::make_pair(0, 2));
+  expected.push_back(std::make_pair(1, 2));
+  expected.push_back(std::make_pair(2, 2));
+  expected.push_back(std::make_pair(3, 2));
+  expected.push_back(std::make_pair(0, 3));
+  expected.push_back(std::make_pair(1, 3));
+  expected.push_back(std::make_pair(2, 3));
+  expected.push_back(std::make_pair(3, 3));
+  expected.push_back(std::make_pair(4, 3));
+  expected.push_back(std::make_pair(0, 4));
+  expected.push_back(std::make_pair(1, 4));
+  expected.push_back(std::make_pair(2, 4));
+  expected.push_back(std::make_pair(3, 4));
+  expected.push_back(std::make_pair(4, 4));
+  expected.push_back(std::make_pair(2, 0));
+  expected.push_back(std::make_pair(3, 0));
+  expected.push_back(std::make_pair(3, 1));
+  expected.push_back(std::make_pair(4, 1));
+  expected.push_back(std::make_pair(4, 0));
+  expected.push_back(std::make_pair(4, 2));
+
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+
+  // Two tile center.
+  center = gfx::Rect(50, 15, 1, 10);
+
+  // Layout of the tiling data, and expected return order:
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0| 20  8  6  4 17
+  //  1| 21  9  *  2 16
+  //  2| 22 10  *  1 15
+  //  3| 23  7  5  3 14
+  //  4| 19 11 12 13 18
+  expected.clear();
+  expected.push_back(std::make_pair(3, 2));
+  expected.push_back(std::make_pair(3, 1));
+  expected.push_back(std::make_pair(3, 3));
+  expected.push_back(std::make_pair(3, 0));
+  expected.push_back(std::make_pair(2, 3));
+  expected.push_back(std::make_pair(2, 0));
+  expected.push_back(std::make_pair(1, 3));
+  expected.push_back(std::make_pair(1, 0));
+  expected.push_back(std::make_pair(1, 1));
+  expected.push_back(std::make_pair(1, 2));
+  expected.push_back(std::make_pair(1, 4));
+  expected.push_back(std::make_pair(2, 4));
+  expected.push_back(std::make_pair(3, 4));
+  expected.push_back(std::make_pair(4, 3));
+  expected.push_back(std::make_pair(4, 2));
+  expected.push_back(std::make_pair(4, 1));
+  expected.push_back(std::make_pair(4, 0));
+  expected.push_back(std::make_pair(4, 4));
+  expected.push_back(std::make_pair(0, 4));
+  expected.push_back(std::make_pair(0, 0));
+  expected.push_back(std::make_pair(0, 1));
+  expected.push_back(std::make_pair(0, 2));
+  expected.push_back(std::make_pair(0, 3));
+
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+}
+
+TEST(TilingDataTest, SpiralDifferenceIteratorWideTilesSmallConsider) {
+  TilingData tiling_data(gfx::Size(20, 10), gfx::Size(100, 50), false);
+  gfx::Rect ignore;
+  std::vector<std::pair<int, int>> expected;
+  gfx::Rect center(30, 15, 1, 1);
+
+  // Consider is one cell.
+  gfx::Rect consider(1, 1);
+
+  // Layout of the tiling data, and expected return order:
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0|  1
+  //  1|     *
+  //  2|
+  //  3|
+  //  4|
+  expected.push_back(std::make_pair(0, 0));
+
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+
+  // Consider is bottom right corner.
+  consider = gfx::Rect(70, 35, 20, 10);
+
+  // Layout of the tiling data, and expected return order:
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0|
+  //  1|     *
+  //  2|
+  //  3|           1  3
+  //  4|           2  4
+  expected.clear();
+  expected.push_back(std::make_pair(3, 3));
+  expected.push_back(std::make_pair(3, 4));
+  expected.push_back(std::make_pair(4, 3));
+  expected.push_back(std::make_pair(4, 4));
+
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+
+  // Consider is one column.
+  consider = gfx::Rect(21, 0, 1, 100);
+
+  // Layout of the tiling data, and expected return order:
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0|     2
+  //  1|     *
+  //  2|     1
+  //  3|     3
+  //  4|     4
+  expected.clear();
+  expected.push_back(std::make_pair(1, 2));
+  expected.push_back(std::make_pair(1, 0));
+  expected.push_back(std::make_pair(1, 3));
+  expected.push_back(std::make_pair(1, 4));
+
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+
+  // Consider is four columns.
+  consider = gfx::Rect(80, 50);
+
+  // Layout of the tiling data, and expected return order:
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0|  7  5  3 14
+  //  1|  8  *  1 13
+  //  2|  6  4  2 12
+  //  3|  9 10 11 15
+  //  4| 16 17 18 19
+  expected.clear();
+  expected.push_back(std::make_pair(2, 1));
+  expected.push_back(std::make_pair(2, 2));
+  expected.push_back(std::make_pair(2, 0));
+  expected.push_back(std::make_pair(1, 2));
+  expected.push_back(std::make_pair(1, 0));
+  expected.push_back(std::make_pair(0, 2));
+  expected.push_back(std::make_pair(0, 0));
+  expected.push_back(std::make_pair(0, 1));
+  expected.push_back(std::make_pair(0, 3));
+  expected.push_back(std::make_pair(1, 3));
+  expected.push_back(std::make_pair(2, 3));
+  expected.push_back(std::make_pair(3, 2));
+  expected.push_back(std::make_pair(3, 1));
+  expected.push_back(std::make_pair(3, 0));
+  expected.push_back(std::make_pair(3, 3));
+  expected.push_back(std::make_pair(0, 4));
+  expected.push_back(std::make_pair(1, 4));
+  expected.push_back(std::make_pair(2, 4));
+  expected.push_back(std::make_pair(3, 4));
+
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+}
+
+TEST(TilingDataTest, SpiralDifferenceIteratorWideTilesHasIgnore) {
+  TilingData tiling_data(gfx::Size(20, 10), gfx::Size(100, 50), false);
+  gfx::Rect consider(100, 50);
+  std::vector<std::pair<int, int>> expected;
+  gfx::Rect center(30, 15, 1, 1);
+
+  // Full ignore.
+  gfx::Rect ignore(100, 50);
+
+  // Layout of the tiling data, and expected return order:
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0|  I  I  I  I  I
+  //  1|  I  *  I  I  I
+  //  2|  I  I  I  I  I
+  //  3|  I  I  I  I  I
+  //  4|  I  I  I  I  I
+  expected.clear();
+
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+
+  // 3 column ignore.
+  ignore = gfx::Rect(30, 0, 40, 100);
+
+  // Layout of the tiling data, and expected return order:
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0|  2  I  I  I  9
+  //  1|  3  *  I  I  8
+  //  2|  1  I  I  I  7
+  //  3|  4  I  I  I  6
+  //  4|  5  I  I  I 10
+  expected.clear();
+
+  expected.push_back(std::make_pair(0, 2));
+  expected.push_back(std::make_pair(0, 0));
+  expected.push_back(std::make_pair(0, 1));
+  expected.push_back(std::make_pair(0, 3));
+  expected.push_back(std::make_pair(0, 4));
+  expected.push_back(std::make_pair(4, 3));
+  expected.push_back(std::make_pair(4, 2));
+  expected.push_back(std::make_pair(4, 1));
+  expected.push_back(std::make_pair(4, 0));
+  expected.push_back(std::make_pair(4, 4));
+
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+
+  // Ignore covers the top half.
+  ignore = gfx::Rect(100, 25);
+
+  // Layout of the tiling data, and expected return order:
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0|  I  I  I  I  I
+  //  1|  I  *  I  I  I
+  //  2|  I  I  I  I  I
+  //  3|  1  2  3  4  9
+  //  4|  5  6  7  8 10
+  expected.clear();
+
+  expected.push_back(std::make_pair(0, 3));
+  expected.push_back(std::make_pair(1, 3));
+  expected.push_back(std::make_pair(2, 3));
+  expected.push_back(std::make_pair(3, 3));
+  expected.push_back(std::make_pair(0, 4));
+  expected.push_back(std::make_pair(1, 4));
+  expected.push_back(std::make_pair(2, 4));
+  expected.push_back(std::make_pair(3, 4));
+  expected.push_back(std::make_pair(4, 3));
+  expected.push_back(std::make_pair(4, 4));
+
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+}
+
+TEST(TilingDataTest, SpiralDifferenceIteratorWideTilesRectangleCenter) {
+  TilingData tiling_data(gfx::Size(20, 10), gfx::Size(100, 50), false);
+  gfx::Rect consider(100, 50);
+  std::vector<std::pair<int, int>> expected;
+  gfx::Rect ignore;
+
+  // Two cell center
+  gfx::Rect center(50, 25, 1, 10);
+
+  // Layout of the tiling data, and expected return order:
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0| 19 13 12 11 18
+  //  1| 20  8  6  4 17
+  //  2| 21  9  *  2 16
+  //  3| 22 10  *  1 15
+  //  4| 23  7  5  3 14
+  expected.clear();
+  expected.push_back(std::make_pair(3, 3));
+  expected.push_back(std::make_pair(3, 2));
+  expected.push_back(std::make_pair(3, 4));
+  expected.push_back(std::make_pair(3, 1));
+  expected.push_back(std::make_pair(2, 4));
+  expected.push_back(std::make_pair(2, 1));
+  expected.push_back(std::make_pair(1, 4));
+  expected.push_back(std::make_pair(1, 1));
+  expected.push_back(std::make_pair(1, 2));
+  expected.push_back(std::make_pair(1, 3));
+  expected.push_back(std::make_pair(3, 0));
+  expected.push_back(std::make_pair(2, 0));
+  expected.push_back(std::make_pair(1, 0));
+  expected.push_back(std::make_pair(4, 4));
+  expected.push_back(std::make_pair(4, 3));
+  expected.push_back(std::make_pair(4, 2));
+  expected.push_back(std::make_pair(4, 1));
+  expected.push_back(std::make_pair(4, 0));
+  expected.push_back(std::make_pair(0, 0));
+  expected.push_back(std::make_pair(0, 1));
+  expected.push_back(std::make_pair(0, 2));
+  expected.push_back(std::make_pair(0, 3));
+  expected.push_back(std::make_pair(0, 4));
+
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+
+  // Three by two center.
+  center = gfx::Rect(30, 25, 40, 10);
+
+  // Layout of the tiling data, and expected return order:
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0| 19 18 17 16 15
+  //  1| 12 10  9  8  4
+  //  2| 13  *  *  *  2
+  //  3| 14  *  *  *  1
+  //  4| 11  5  6  7  3
+  expected.clear();
+
+  expected.push_back(std::make_pair(4, 3));
+  expected.push_back(std::make_pair(4, 2));
+  expected.push_back(std::make_pair(4, 4));
+  expected.push_back(std::make_pair(4, 1));
+  expected.push_back(std::make_pair(1, 4));
+  expected.push_back(std::make_pair(2, 4));
+  expected.push_back(std::make_pair(3, 4));
+  expected.push_back(std::make_pair(3, 1));
+  expected.push_back(std::make_pair(2, 1));
+  expected.push_back(std::make_pair(1, 1));
+  expected.push_back(std::make_pair(0, 4));
+  expected.push_back(std::make_pair(0, 1));
+  expected.push_back(std::make_pair(0, 2));
+  expected.push_back(std::make_pair(0, 3));
+  expected.push_back(std::make_pair(4, 0));
+  expected.push_back(std::make_pair(3, 0));
+  expected.push_back(std::make_pair(2, 0));
+  expected.push_back(std::make_pair(1, 0));
+  expected.push_back(std::make_pair(0, 0));
+
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+
+  // Column center off the left side.
+  center = gfx::Rect(-100, 0, 60, 50);
+
+  // Layout of the tiling data, and expected return order:
+  //          x  0  1  2  3  4
+  //         y.---------------
+  //  *      0|  5 10 15 20 25
+  //  *      1|  4  9 14 19 24
+  //  *      2|  3  8 13 18 23
+  //  *      3|  2  7 12 17 22
+  //  *      4|  1  6 11 16 21
+  expected.clear();
+
+  expected.push_back(std::make_pair(0, 4));
+  expected.push_back(std::make_pair(0, 3));
+  expected.push_back(std::make_pair(0, 2));
+  expected.push_back(std::make_pair(0, 1));
+  expected.push_back(std::make_pair(0, 0));
+  expected.push_back(std::make_pair(1, 4));
+  expected.push_back(std::make_pair(1, 3));
+  expected.push_back(std::make_pair(1, 2));
+  expected.push_back(std::make_pair(1, 1));
+  expected.push_back(std::make_pair(1, 0));
+  expected.push_back(std::make_pair(2, 4));
+  expected.push_back(std::make_pair(2, 3));
+  expected.push_back(std::make_pair(2, 2));
+  expected.push_back(std::make_pair(2, 1));
+  expected.push_back(std::make_pair(2, 0));
+  expected.push_back(std::make_pair(3, 4));
+  expected.push_back(std::make_pair(3, 3));
+  expected.push_back(std::make_pair(3, 2));
+  expected.push_back(std::make_pair(3, 1));
+  expected.push_back(std::make_pair(3, 0));
+  expected.push_back(std::make_pair(4, 4));
+  expected.push_back(std::make_pair(4, 3));
+  expected.push_back(std::make_pair(4, 2));
+  expected.push_back(std::make_pair(4, 1));
+  expected.push_back(std::make_pair(4, 0));
+
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+}
+
+TEST(TilingDataTest, SpiralDifferenceIteratorWideTilesEdgeCases) {
+  TilingData tiling_data(gfx::Size(20, 10), gfx::Size(100, 50), false);
+  std::vector<std::pair<int, int>> expected;
+  gfx::Rect center;
+  gfx::Rect consider;
+  gfx::Rect ignore;
+
+  // Ignore contains, but is not equal to, consider and center.
+  ignore = gfx::Rect(70, 0, 40, 50);
+  consider = gfx::Rect(80, 20, 20, 30);
+  center = gfx::Rect(90, 0, 5, 5);
+
+  // Layout of the tiling data, and expected return order:
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0|           I  *
+  //  1|           I  I
+  //  2|           I  I
+  //  3|           I  I
+  //  4|           I  I
+  expected.clear();
+
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+
+  // Center intersects with consider.
+  ignore = gfx::Rect();
+  center = gfx::Rect(0, 30, 100, 20);
+  consider = gfx::Rect(40, 50);
+
+  // Layout of the tiling data, and expected return order:
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0|  6  5
+  //  1|  4  3
+  //  2|  2  1
+  //  3|  *  *  *  *  *
+  //  4|  *  *  *  *  *
+  expected.clear();
+
+  expected.push_back(std::make_pair(1, 2));
+  expected.push_back(std::make_pair(0, 2));
+  expected.push_back(std::make_pair(1, 1));
+  expected.push_back(std::make_pair(0, 1));
+  expected.push_back(std::make_pair(1, 0));
+  expected.push_back(std::make_pair(0, 0));
+
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+
+  // Consider and ignore are non-intersecting.
+  ignore = gfx::Rect(30, 50);
+  consider = gfx::Rect(60, 0, 30, 50);
+  center = gfx::Rect(50, 0, 1, 1);
+
+  // Layout of the tiling data, and expected return order:
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0|  I  I  *  1  5
+  //  1|  I  I     2  4
+  //  2|  I  I     3  6
+  //  3|  I  I     7  8
+  //  4|  I  I     9 10
+  expected.clear();
+
+  expected.push_back(std::make_pair(3, 0));
+  expected.push_back(std::make_pair(3, 1));
+  expected.push_back(std::make_pair(3, 2));
+  expected.push_back(std::make_pair(4, 1));
+  expected.push_back(std::make_pair(4, 0));
+  expected.push_back(std::make_pair(4, 2));
+  expected.push_back(std::make_pair(3, 3));
+  expected.push_back(std::make_pair(4, 3));
+  expected.push_back(std::make_pair(3, 4));
+  expected.push_back(std::make_pair(4, 4));
+
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+
+  // Center intersects with ignore.
+  consider = gfx::Rect(100, 50);
+  center = gfx::Rect(50, 0, 1, 50);
+  ignore = gfx::Rect(0, 25, 100, 1);
+
+  // Layout of the tiling data, and expected return order:
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0| 13  5  *  4 12
+  //  1| 14  6  *  3 11
+  //  2|  I  I  *  I  I
+  //  3| 15  7  *  2 10
+  //  4| 16  8  *  1  9
+  expected.clear();
+
+  expected.push_back(std::make_pair(3, 4));
+  expected.push_back(std::make_pair(3, 3));
+  expected.push_back(std::make_pair(3, 1));
+  expected.push_back(std::make_pair(3, 0));
+  expected.push_back(std::make_pair(1, 0));
+  expected.push_back(std::make_pair(1, 1));
+  expected.push_back(std::make_pair(1, 3));
+  expected.push_back(std::make_pair(1, 4));
+  expected.push_back(std::make_pair(4, 4));
+  expected.push_back(std::make_pair(4, 3));
+  expected.push_back(std::make_pair(4, 1));
+  expected.push_back(std::make_pair(4, 0));
+  expected.push_back(std::make_pair(0, 0));
+  expected.push_back(std::make_pair(0, 1));
+  expected.push_back(std::make_pair(0, 3));
+  expected.push_back(std::make_pair(0, 4));
+
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+
+  // Center and ignore are the same.
+  consider = gfx::Rect(100, 50);
+  center = gfx::Rect(50, 0, 1, 50);
+  ignore = center;
+
+  // Layout of the tiling data, and expected return order:
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0| 16  6  *  5 15
+  //  1| 17  7  *  4 14
+  //  2| 18  8  *  3 13
+  //  3| 19  9  *  2 12
+  //  4| 20 10  *  1 11
+  expected.clear();
+
+  expected.push_back(std::make_pair(3, 4));
+  expected.push_back(std::make_pair(3, 3));
+  expected.push_back(std::make_pair(3, 2));
+  expected.push_back(std::make_pair(3, 1));
+  expected.push_back(std::make_pair(3, 0));
+  expected.push_back(std::make_pair(1, 0));
+  expected.push_back(std::make_pair(1, 1));
+  expected.push_back(std::make_pair(1, 2));
+  expected.push_back(std::make_pair(1, 3));
+  expected.push_back(std::make_pair(1, 4));
+  expected.push_back(std::make_pair(4, 4));
+  expected.push_back(std::make_pair(4, 3));
+  expected.push_back(std::make_pair(4, 2));
+  expected.push_back(std::make_pair(4, 1));
+  expected.push_back(std::make_pair(4, 0));
+  expected.push_back(std::make_pair(0, 0));
+  expected.push_back(std::make_pair(0, 1));
+  expected.push_back(std::make_pair(0, 2));
+  expected.push_back(std::make_pair(0, 3));
+  expected.push_back(std::make_pair(0, 4));
+
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+
+  // Empty tiling data.
+  TilingData empty_data(gfx::Size(0, 0), gfx::Size(0, 0), false);
+
+  expected.clear();
+  TestSpiralIterate(__LINE__, empty_data, consider, ignore, center, expected);
+
+  // Empty consider.
+  ignore = gfx::Rect();
+  center = gfx::Rect(1, 1, 1, 1);
+  consider = gfx::Rect();
+
+  expected.clear();
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+
+  // Empty center. Note: This arbitrarily puts the center to be off the top-left
+  // corner.
+  consider = gfx::Rect(100, 50);
+  ignore = gfx::Rect();
+  center = gfx::Rect();
+
+  // Layout of the tiling data, and expected return order:
+  //   x  0  1  2  3  4
+  //  y.---------------
+  //  0|  1  3 11 19 24
+  //  1|  2  4 10 18 23
+  //  2|  5  6 12 17 22
+  //  3|  7  8  9 20 21
+  //  4| 13 14 15 16 25
+  expected.clear();
+
+  expected.push_back(std::make_pair(0, 0));
+  expected.push_back(std::make_pair(0, 1));
+  expected.push_back(std::make_pair(1, 0));
+  expected.push_back(std::make_pair(1, 1));
+  expected.push_back(std::make_pair(0, 2));
+  expected.push_back(std::make_pair(1, 2));
+  expected.push_back(std::make_pair(0, 3));
+  expected.push_back(std::make_pair(1, 3));
+  expected.push_back(std::make_pair(2, 3));
+  expected.push_back(std::make_pair(2, 1));
+  expected.push_back(std::make_pair(2, 0));
+  expected.push_back(std::make_pair(2, 2));
+  expected.push_back(std::make_pair(0, 4));
+  expected.push_back(std::make_pair(1, 4));
+  expected.push_back(std::make_pair(2, 4));
+  expected.push_back(std::make_pair(3, 4));
+  expected.push_back(std::make_pair(3, 2));
+  expected.push_back(std::make_pair(3, 1));
+  expected.push_back(std::make_pair(3, 0));
+  expected.push_back(std::make_pair(3, 3));
+  expected.push_back(std::make_pair(4, 3));
+  expected.push_back(std::make_pair(4, 2));
+  expected.push_back(std::make_pair(4, 1));
+  expected.push_back(std::make_pair(4, 0));
+  expected.push_back(std::make_pair(4, 4));
+
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+
+  // Every rect is empty.
+  ignore = gfx::Rect();
+  center = gfx::Rect();
+  consider = gfx::Rect();
+
+  expected.clear();
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+
+  // Center is just to the left of cover, and off of the tiling's left side.
+  consider = gfx::Rect(100, 50);
+  ignore = gfx::Rect();
+  center = gfx::Rect(-40, 0, 39, 50);
+
+  // Layout of the tiling data, and expected return order:
+  //    x  0  1  2  3  4
+  //   y.---------------
+  // * 0|  5 10 15 20 25
+  // * 1|  4  9 14 19 24
+  // * 2|  3  8 13 18 23
+  // * 3|  2  7 12 17 22
+  // * 4|  1  6 11 16 21
+  expected.clear();
+
+  expected.push_back(std::make_pair(0, 4));
+  expected.push_back(std::make_pair(0, 3));
+  expected.push_back(std::make_pair(0, 2));
+  expected.push_back(std::make_pair(0, 1));
+  expected.push_back(std::make_pair(0, 0));
+  expected.push_back(std::make_pair(1, 4));
+  expected.push_back(std::make_pair(1, 3));
+  expected.push_back(std::make_pair(1, 2));
+  expected.push_back(std::make_pair(1, 1));
+  expected.push_back(std::make_pair(1, 0));
+  expected.push_back(std::make_pair(2, 4));
+  expected.push_back(std::make_pair(2, 3));
+  expected.push_back(std::make_pair(2, 2));
+  expected.push_back(std::make_pair(2, 1));
+  expected.push_back(std::make_pair(2, 0));
+  expected.push_back(std::make_pair(3, 4));
+  expected.push_back(std::make_pair(3, 3));
+  expected.push_back(std::make_pair(3, 2));
+  expected.push_back(std::make_pair(3, 1));
+  expected.push_back(std::make_pair(3, 0));
+  expected.push_back(std::make_pair(4, 4));
+  expected.push_back(std::make_pair(4, 3));
+  expected.push_back(std::make_pair(4, 2));
+  expected.push_back(std::make_pair(4, 1));
+  expected.push_back(std::make_pair(4, 0));
+
+  TestSpiralIterate(__LINE__, tiling_data, consider, ignore, center, expected);
+}
+
 }  // namespace
 
 }  // namespace cc