cc: Remove and Create the correct tiles when resizing live tiles rect

cc/resources/picture_layer_tiling.cc

Index: cc/resources/picture_layer_tiling.cc
diff --git a/cc/resources/picture_layer_tiling.cc b/cc/resources/picture_layer_tiling.cc
index 3d132e162c7aca32e1b41ff875808962933fab50..3d05ee656cf04751de8a3b5170a912563e15a873 100644
--- a/cc/resources/picture_layer_tiling.cc
+++ b/cc/resources/picture_layer_tiling.cc
@@ -533,10 +533,14 @@ void PictureLayerTiling::UpdateTilePriorities(
     tile->set_is_occluded(tree, is_occluded);
   }
 
-  // Assign soon priority to skewport tiles.
+  // Assign soon priority to skewport tiles. Include borders to also prioritize
+  // tiles whose borders are in the skewport, and to exclude tiles whose borders
+  // are in the visible rect, since those are handled above.
   has_skewport_rect_tiles_ = false;
-  for (TilingData::DifferenceIterator iter(
-           &tiling_data_, skewport, visible_rect_in_content_space);
+  for (TilingData::DifferenceIterator iter(&tiling_data_,
+                                           skewport,
+                                           visible_rect_in_content_space,
+                                           include_borders);
        iter;
        ++iter) {
     TileMap::iterator find = tiles_.find(iter.index());
@@ -556,10 +560,12 @@ void PictureLayerTiling::UpdateTilePriorities(
     tile->SetPriority(tree, priority);
   }
 
-  // Assign eventually priority to interest rect tiles.
+  // Assign eventually priority to interest rect tiles. Include borders to
+  // also prioritize tiles whose borders are in the eventually rect and exclude
+  // tiles whose borders are in the skewport, as those are handled above.
   has_eventually_rect_tiles_ = false;
   for (TilingData::DifferenceIterator iter(
-           &tiling_data_, eventually_rect, skewport);
+           &tiling_data_, eventually_rect, skewport, include_borders);
        iter;
        ++iter) {
     TileMap::iterator find = tiles_.find(iter.index());
@@ -579,13 +585,15 @@ void PictureLayerTiling::UpdateTilePriorities(
     tile->SetPriority(tree, priority);
   }
 
-  // Upgrade the priority on border tiles to be SOON.
+  // Upgrade the priority on border tiles to be SOON. Include borders to include
+  // tiles whose borders are in the soon_border_rect and exclude those with
+  // borders in the skewport, as those are handled above.
   gfx::Rect soon_border_rect = visible_rect_in_content_space;
   float border = kSoonBorderDistanceInScreenPixels / content_to_screen_scale;
   soon_border_rect.Inset(-border, -border, -border, -border);
   has_soon_border_rect_tiles_ = false;
   for (TilingData::DifferenceIterator iter(
-           &tiling_data_, soon_border_rect, skewport);
+           &tiling_data_, soon_border_rect, skewport, include_borders);
        iter;
        ++iter) {
     TileMap::iterator find = tiles_.find(iter.index());
@@ -616,10 +624,14 @@ void PictureLayerTiling::SetLiveTilesRect(
   if (live_tiles_rect_ == new_live_tiles_rect)
     return;
 
-  // Iterate to delete all tiles outside of our new live_tiles rect.
+  // Iterate to delete all tiles outside of our new live_tiles rect. Iterate
+  // without borders to avoid including tiles that have only border pixels
+  // outside the new live tiles rect.
+  bool include_borders = false;
   for (TilingData::DifferenceIterator iter(&tiling_data_,
                                            live_tiles_rect_,
-                                           new_live_tiles_rect);
+                                           new_live_tiles_rect,
+                                           include_borders);
        iter;
        ++iter) {
     TileMapKey key(iter.index());
@@ -635,9 +647,12 @@ void PictureLayerTiling::SetLiveTilesRect(
   const PictureLayerTiling* twin_tiling = client_->GetTwinTiling(this);
 
   // Iterate to allocate new tiles for all regions with newly exposed area.
+  // Do the iteration without borders to avoid adding tiles that already exist
+  // for tiles whose border pixels are in the new live tiles rect.
   for (TilingData::DifferenceIterator iter(&tiling_data_,
                                            new_live_tiles_rect,
-                                           live_tiles_rect_);
+                                           live_tiles_rect_,
+                                           include_borders);
        iter;
        ++iter) {
     TileMapKey key(iter.index());