implement the logic to set tile priorities based on current matrix

cc/picture_layer_tiling_unittest.cc

 // 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/picture_layer_tiling.h"
 
 #include "cc/test/fake_picture_layer_tiling_client.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/gfx/size_conversions.h"
 
@@ skipping 46 matching lines @@
     EXPECT_TRUE(remaining.IsEmpty());
   }
 
  protected:
   FakePictureLayerTilingClient client_;
   scoped_ptr<PictureLayerTiling> tiling_;
 
   DISALLOW_COPY_AND_ASSIGN(PictureLayerTilingIteratorTest);
 };
 
+class PictureLayerTilingTest : public testing::Test {
+ public:
+  PictureLayerTilingTest() {
+    tiling_ = PictureLayerTiling::Create(0, gfx::Size(0, 0));
+  }
+
+  void VerifyTimeForBoundsToIntersect(gfx::Rect previous,
+                                      gfx::Rect current,
+                                      gfx::Rect target,
+                                      double time) {
+    EXPECT_EQ(tiling_->TimeForBoundsToIntersect(previous, current, 1, target),
+              time);
+  }
+ protected:
+  scoped_ptr<PictureLayerTiling> tiling_;
+};
+
 TEST_F(PictureLayerTilingIteratorTest, IteratorCoversLayerBoundsNoScale) {
   Initialize(gfx::Size(100, 100), 1, gfx::Size(1099, 801));
   VerifyTilesExactlyCoverRect(1, gfx::Rect());
   VerifyTilesExactlyCoverRect(1, gfx::Rect(0, 0, 1099, 801));
   VerifyTilesExactlyCoverRect(1, gfx::Rect(52, 83, 789, 412));
 
   // With borders, a size of 3x3 = 1 pixel of content.
   Initialize(gfx::Size(3, 3), 1, gfx::Size(10, 10));
   VerifyTilesExactlyCoverRect(1, gfx::Rect(0, 0, 1, 1));
   VerifyTilesExactlyCoverRect(1, gfx::Rect(0, 0, 2, 2));
@@ skipping 34 matching lines @@
   VerifyTilesExactlyCoverRect(2.0f, gfx::Rect(512, 365, 253, 182));
 
   float scale = 6.7f;
   gfx::Size bounds(800, 600);
   gfx::Rect full_rect(gfx::ToCeiledSize(gfx::ScaleSize(bounds, scale)));
   Initialize(gfx::Size(256, 512), 5.2f, bounds);
   VerifyTilesExactlyCoverRect(scale, full_rect);
   VerifyTilesExactlyCoverRect(scale, gfx::Rect(2014, 1579, 867, 1033));
 }
 
+TEST_F(PictureLayerTilingTest, 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(PictureLayerTilingTest, 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