cc: Fix layer raster tile iterator not to skip a tile erroneously.

cc/layers/picture_layer_impl_unittest.cc

Index: cc/layers/picture_layer_impl_unittest.cc
diff --git a/cc/layers/picture_layer_impl_unittest.cc b/cc/layers/picture_layer_impl_unittest.cc
index bd6a8f7f479f7fd466a466cfadcbf30597a07103..f72abfbe7f1296ddab3d348b3587065b4da2177f 100644
--- a/cc/layers/picture_layer_impl_unittest.cc
+++ b/cc/layers/picture_layer_impl_unittest.cc
@@ -2498,6 +2498,11 @@ TEST_F(PictureLayerImplTest, HighResTilingDuringAnimationForGpuRasterization) {
 }
 
 TEST_F(PictureLayerImplTest, LayerRasterTileIterator) {
+  base::TimeTicks time_ticks;
+  time_ticks += base::TimeDelta::FromMilliseconds(1);
+  host_impl_.SetCurrentBeginFrameArgs(
+      CreateBeginFrameArgsForTesting(time_ticks));
+
   gfx::Size tile_size(100, 100);
   gfx::Size layer_bounds(1000, 1000);
 
@@ -2563,6 +2568,74 @@ TEST_F(PictureLayerImplTest, LayerRasterTileIterator) {
   EXPECT_EQ(low_res_tile_count + high_res_tile_count + non_ideal_tile_count,
             unique_tiles.size());
 
+  time_ticks += base::TimeDelta::FromMilliseconds(200);
+  host_impl_.SetCurrentBeginFrameArgs(
+      CreateBeginFrameArgsForTesting(time_ticks));
+
+  gfx::Rect viewport = gfx::Rect(1100, 1100, 500, 500);
+  gfx::Transform transform;
+  bool resourceless_software_draw = false;
+  host_impl_.SetExternalDrawConstraints(transform,

[vmpstr, 2014/09/09 17:37:35]

nit: Does host_impl_.SetViewportSize work here instead? If so, use that instead.

[USE eero AT chromium.org, 2014/09/10 07:48:19]

I don't see how as it is not about size but position.
That is to say I have to somehow move the viewport out of layer bounds in order
to prevent NOW tiles from being created.

Or maybe an occlusion tracker could be used?

+                                        viewport,
+                                        viewport,
+                                        viewport,
+                                        transform,
+                                        resourceless_software_draw);
+  pending_layer_->draw_properties().visible_content_rect = viewport;
+  pending_layer_->draw_properties().screen_space_transform = transform;

[vmpstr, 2014/09/09 17:37:35]

I don't think you need this?

[USE eero AT chromium.org, 2014/09/10 07:48:19]

I'll check.

+  pending_layer_->UpdateTiles(NULL);
+
+  unique_tiles.clear();
+  reached_prepaint = false;
+  non_ideal_tile_count = 0u;
+  low_res_tile_count = 0u;
+  high_res_tile_count = 0u;
+  for (it = PictureLayerImpl::LayerRasterTileIterator(pending_layer_, false);
+       it;
+       ++it) {
+    Tile* tile = *it;
+    TilePriority priority = tile->priority(PENDING_TREE);
+
+    EXPECT_TRUE(tile);
+
+    // Non-high res tiles only get visible tiles. Also, prepaint should only
+    // come at the end of the iteration.
+    if (priority.resolution != HIGH_RESOLUTION)
+      EXPECT_EQ(TilePriority::NOW, priority.priority_bin);
+    else if (reached_prepaint)
+      EXPECT_NE(TilePriority::NOW, priority.priority_bin);
+    else
+      reached_prepaint = priority.priority_bin != TilePriority::NOW;
+
+    non_ideal_tile_count += priority.resolution == NON_IDEAL_RESOLUTION;
+    low_res_tile_count += priority.resolution == LOW_RESOLUTION;
+    high_res_tile_count += priority.resolution == HIGH_RESOLUTION;
+
+    unique_tiles.insert(tile);
+  }
+
+  EXPECT_TRUE(reached_prepaint);
+  EXPECT_EQ(0u, non_ideal_tile_count);
+  EXPECT_EQ(0u, low_res_tile_count);
+  EXPECT_EQ(16u, high_res_tile_count);

[USE eero AT chromium.org, 2014/09/09 17:13:45]

Without the fix, the iterator returns only 15 high resolution tiles.

[vmpstr, 2014/09/09 17:37:35]

These are non-now ones, right?

[USE eero AT chromium.org, 2014/09/10 07:48:19]

Yes, correct.

+  EXPECT_EQ(low_res_tile_count + high_res_tile_count + non_ideal_tile_count,
+            unique_tiles.size());
+
+  time_ticks += base::TimeDelta::FromMilliseconds(200);
+  host_impl_.SetCurrentBeginFrameArgs(
+      CreateBeginFrameArgsForTesting(time_ticks));
+
+  viewport = gfx::Rect(0, 0, 500, 500);
+  host_impl_.SetExternalDrawConstraints(transform,

[vmpstr, 2014/09/09 17:37:35]

Same comments here as above

[USE eero AT chromium.org, 2014/09/10 07:48:19]

And the same reply.

+                                        viewport,
+                                        viewport,
+                                        viewport,
+                                        transform,
+                                        resourceless_software_draw);
+  pending_layer_->draw_properties().visible_content_rect = viewport;
+  pending_layer_->draw_properties().screen_space_transform = transform;
+  pending_layer_->UpdateTiles(NULL);
+
   std::vector<Tile*> high_res_tiles = high_res_tiling->AllTilesForTesting();
   for (std::vector<Tile*>::iterator tile_it = high_res_tiles.begin();
        tile_it != high_res_tiles.end();