cc: Fix tile priority inversion in picture layer tiling.

cc/tiles/picture_layer_tiling_unittest.cc

Index: cc/tiles/picture_layer_tiling_unittest.cc
diff --git a/cc/tiles/picture_layer_tiling_unittest.cc b/cc/tiles/picture_layer_tiling_unittest.cc
index 147f836a5974171a3951cb7ebbde6dea00928981..3913c105193198ae386a1d05f626a02ed79d2c23 100644
--- a/cc/tiles/picture_layer_tiling_unittest.cc
+++ b/cc/tiles/picture_layer_tiling_unittest.cc
@@ -61,9 +61,13 @@ class TestablePictureLayerTiling : public PictureLayerTiling {
   }
 
   gfx::Rect live_tiles_rect() const { return live_tiles_rect_; }
+  PriorityRectType visible_rect_type() const {
+    return PriorityRectType::VISIBLE_RECT;
+  }
 
   using PictureLayerTiling::RemoveTileAt;
   using PictureLayerTiling::RemoveTilesInRegion;
+  using PictureLayerTiling::ComputePriorityRectTypeForTile;
 
  protected:
   TestablePictureLayerTiling(WhichTree tree,
@@ -955,6 +959,30 @@ TEST(PictureLayerTilingTest, RecycledTilesClearedOnReset) {
   EXPECT_FALSE(recycle_tiling->TileAt(0, 0));
 }
 
+TEST(PictureLayerTilingTest, EdgeCaseTileNowAndRequired) {
+  FakePictureLayerTilingClient pending_client;
+  pending_client.SetTileSize(gfx::Size(100, 100));
+
+  scoped_refptr<FakeRasterSource> raster_source =
+      FakeRasterSource::CreateFilled(gfx::Size(500, 500));
+  std::unique_ptr<TestablePictureLayerTiling> pending_tiling =
+      TestablePictureLayerTiling::Create(PENDING_TREE, 1.0f, raster_source,
+                                         &pending_client, LayerTreeSettings());
+  pending_tiling->set_resolution(HIGH_RESOLUTION);
+  pending_tiling->set_can_require_tiles_for_activation(true);
+
+  gfx::Rect visible_rect = gfx::Rect(0, 0, 99, 99);

[danakj, 2017/01/30 16:55:18]

Can you also test what happens when the tile is 1px inside the rect?

[vmpstr, 2017/01/30 19:38:20]

Done.

+  gfx::Rect eventually_rect = gfx::Rect(0, 0, 500, 500);
+  pending_tiling->ComputeTilePriorityRects(visible_rect, visible_rect,
+                                           visible_rect, eventually_rect, 1.f,
+                                           Occlusion());
+
+  Tile* tile = pending_tiling->TileAt(1, 0);

[danakj, 2017/01/30 16:55:18]

Can you do some expectations to prove that the tile is on the edge of the
visible rect and border overlaps it?

[vmpstr, 2017/01/30 19:38:20]

Done.

+  EXPECT_NE(pending_tiling->visible_rect_type(),
+            pending_tiling->ComputePriorityRectTypeForTile(tile));
+  EXPECT_FALSE(pending_tiling->IsTileRequiredForActivation(tile));
+}
+
 TEST_F(PictureLayerTilingIteratorTest, ResizeTilesAndUpdateToCurrent) {
   // The tiling has four rows and three columns.
   Initialize(gfx::Size(150, 100), 1.f, gfx::Size(250, 150));