Split picture layer quads to allow removing more occluded area.

cc/trees/occlusion_unittest.cc

Index: cc/trees/occlusion_unittest.cc
diff --git a/cc/trees/occlusion_unittest.cc b/cc/trees/occlusion_unittest.cc
index da2f6fd0b6ebece769eac89ba4e74ffdbc70d8bc..caaaa506c5b1275527c572d5207efd6d711deab7 100644
--- a/cc/trees/occlusion_unittest.cc
+++ b/cc/trees/occlusion_unittest.cc
@@ -6,6 +6,7 @@
 
 #include <stddef.h>
 
+#include "cc/base/region.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace cc {
@@ -270,5 +271,49 @@ TEST(OcclusionTest, GetUnoccludedContentRectTranslated) {
   EXPECT_EQ(gfx::Rect(10, 0, 10, 10), half_query_result_down);
 }
 
+TEST(OcclusionTest, OccludeContentRegionScaled) {
+  gfx::Transform half_scale;
+  half_scale.Scale(0.5, 0.5);
+
+  gfx::Transform double_scale;
+  double_scale.Scale(2, 2);
+
+  Occlusion some_occluded_half(half_scale, SimpleEnclosedRegion(5, 5),
+                               SimpleEnclosedRegion(5, 5, 5, 5));
+  Occlusion some_occluded_double(double_scale, SimpleEnclosedRegion(20, 20),
+                                 SimpleEnclosedRegion(19, 20, 21, 20));
+
+  Region region_half(gfx::Rect(5, 0, 15, 20));
+  some_occluded_half.OccludeContentRegion(&region_half);
+
+  Region result_region;
+  // Top right and bottom left rectangles should remain.
+  result_region.Union(gfx::Rect(10, 0, 10, 10));
+  result_region.Union(gfx::Rect(5, 10, 5, 10));
+  EXPECT_EQ(result_region.ToString(), region_half.ToString());
+
+  // The result should be the same as above, as the additional half-pixel
+  // occlusion should be ignored.
+  Region region_double(gfx::Rect(5, 0, 15, 20));
+  some_occluded_double.OccludeContentRegion(&region_double);
+  EXPECT_EQ(result_region.ToString(), region_double.ToString());
+}
+
+TEST(OcclusionTest, OccludeContentRegionRotate) {
+  gfx::Transform rotate_transform;
+  // Extremely small rotation.
+  rotate_transform.Rotate(1);
+
+  Occlusion occlusion(rotate_transform, SimpleEnclosedRegion(10, 10),
+                      SimpleEnclosedRegion(10, 10, 10, 10));
+
+  Region region(gfx::Rect(1, 1, 1, 1));
+  Region occluded_region(region);
+  occlusion.OccludeContentRegion(&occluded_region);
+
+  // Transform isn't axis-aligned, so no occlusion should be done.
+  EXPECT_EQ(region.ToString(), occluded_region.ToString());
+}
+
 }  // namespace
 }  // namespace cc