cc: Don't consider tiles at the layers raster_contents_scale incomplete

cc/layers/picture_layer_impl.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/layers/picture_layer_impl.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "base/debug/trace_event_argument.h"
@@ skipping 280 matching lines @@
     bool has_draw_quad = false;
     if (*iter && iter->IsReadyToDraw()) {
       const ManagedTileState::TileVersion& tile_version =
           iter->GetTileVersionForDrawing();
       switch (tile_version.mode()) {
         case ManagedTileState::TileVersion::RESOURCE_MODE: {
           gfx::RectF texture_rect = iter.texture_rect();
           gfx::Rect opaque_rect = iter->opaque_rect();
           opaque_rect.Intersect(geometry_rect);
 
-          if (iter->contents_scale() != ideal_contents_scale_ &&
+          // The raster_contents_scale_ is the best scale that the layer is
+          // trying to produce, even though it may not be ideal. Since that's
+          // the best the layer can promise in the future, consider those as
+          // complete. But if a tile is ideal scale, we don't want to consider
+          // it incomplete and trying to replace it with a tile at a worse
+          // scale.
+          if (iter->contents_scale() != raster_contents_scale_ &&
+              iter->contents_scale() != ideal_contents_scale_ &&
               geometry_rect.Intersects(scaled_viewport_for_tile_priority)) {
             append_quads_data->num_incomplete_tiles++;
           }
 
           TileDrawQuad* quad =
               render_pass->CreateAndAppendDrawQuad<TileDrawQuad>();
           quad->SetNew(shared_quad_state,
                        geometry_rect,
                        opaque_rect,
                        visible_geometry_rect,
@@ skipping 1432 matching lines @@
       PictureLayerTilingSet::TilingRange tiling_range = CurrentTilingRange();
       size_t current_tiling_range_offset = current_tiling_ - tiling_range.start;
       return tiling_range.end - 1 - current_tiling_range_offset;
     }
   }
   NOTREACHED();
   return 0;
 }
 
 }  // namespace cc