implement the logic to set tile priorities based on current matrix

cc/tile_priority_unittest.cc

Index: cc/tile_priority_unittest.cc
diff --git a/cc/tile_priority_unittest.cc b/cc/tile_priority_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ce1383f9ca11a10352e4e9cbdfa127db5ccc2ef6
--- /dev/null
+++ b/cc/tile_priority_unittest.cc
@@ -0,0 +1,62 @@
+// Copyright 2012 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/tile_priority.h"
+
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace cc {
+
+class TilePriorityTest : public testing::Test {
+ public:
+  TilePriorityTest() {}
+
+  void VerifyTimeForBoundsToIntersect(gfx::Rect previous,
+                                      gfx::Rect current,
+                                      gfx::Rect target,
+                                      double time) {
+    EXPECT_EQ(time, TilePriority::TimeForBoundsToIntersect(
+        previous, current, 1, target));
+  }
+};
+
+TEST_F(TilePriorityTest, TimeForBoundsToIntersectWithScroll) {
+  gfx::Rect target(0, 0, 800, 600);
+  gfx::Rect current(100, 100, 100, 100);
+  VerifyTimeForBoundsToIntersect(
+      gfx::Rect(-200, 0, 100, 100), current, target, 0);
+  VerifyTimeForBoundsToIntersect(
+      gfx::Rect(-100, 0, 100, 100), current, target, 0);
+  VerifyTimeForBoundsToIntersect(
+      gfx::Rect(400, 400, 100, 100), current, target, 0);
+
+  current = gfx::Rect(-300, -300, 100, 100);
+  VerifyTimeForBoundsToIntersect(
+      gfx::Rect(0, 0, 100, 100), current, target, 1000);
+  VerifyTimeForBoundsToIntersect(
+      gfx::Rect(-200, -200, 100, 100), current, target, 1000);
+  VerifyTimeForBoundsToIntersect(
+      gfx::Rect(-400, -400, 100, 100), current, target, 2);
+}
+
+TEST_F(TilePriorityTest, TimeForBoundsToIntersectWithScale) {
+  gfx::Rect target(0, 0, 800, 600);
+  gfx::Rect current(100, 100, 100, 100);
+  VerifyTimeForBoundsToIntersect(
+      gfx::Rect(-200, 0, 200, 200), current, target, 0);
+  VerifyTimeForBoundsToIntersect(
+      gfx::Rect(-100, 0, 50, 50), current, target, 0);
+  VerifyTimeForBoundsToIntersect(
+      gfx::Rect(400, 400, 400, 400), current, target, 0);
+
+  current = gfx::Rect(-300, -300, 100, 100);
+  VerifyTimeForBoundsToIntersect(
+      gfx::Rect(-400, -400, 300, 300), current, target, 1000);
+  VerifyTimeForBoundsToIntersect(
+      gfx::Rect(-275, -275, 50, 50), current, target, 8);
+  VerifyTimeForBoundsToIntersect(
+      gfx::Rect(-450, -450, 50, 50), current, target, 1);
+}
+
+}  // namespace cc