Make tile size a function of the device scale factor.

cc/trees/layer_tree_settings.h

 // Copyright 2011 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.
 
 #ifndef CC_TREES_LAYER_TREE_SETTINGS_H_
 #define CC_TREES_LAYER_TREE_SETTINGS_H_
 
 #include <stddef.h>
 
 #include <vector>
@@ skipping 53 matching lines @@
   int scrollbar_fade_duration_ms = 0;
   SkColor solid_color_scrollbar_color = SK_ColorWHITE;
   bool timeout_and_draw_when_animation_checkerboards = true;
   bool layer_transforms_should_scale_layer_contents = false;
   bool layers_always_allowed_lcd_text = false;
   float minimum_contents_scale = 0.0625f;
   float low_res_contents_scale_factor = 0.25f;
   float top_controls_show_threshold = 0.5f;
   float top_controls_hide_threshold = 0.5f;
   double background_animation_rate = 1.0;
-  gfx::Size default_tile_size;
-  gfx::Size max_untiled_layer_size;
+  bool use_viewport_for_tile_size = false;
   gfx::Size minimum_occlusion_tracking_size;
   // 3000 pixels should give sufficient area for prepainting.
   // Note this value is specified with an ideal contents scale in mind. That
   // is, the ideal tiling would use this value as the padding.
   // TODO(vmpstr): Figure out a better number that doesn't depend on scale.
   int tiling_interest_area_padding = 3000;
   float skewport_target_time_in_seconds = 1.0f;
   int skewport_extrapolation_limit_in_screen_pixels = 2000;
   size_t max_memory_for_prepaint_percentage = 100;
   bool use_zero_copy = false;
@@ skipping 18 matching lines @@
   // If set to true, the display item list will internally cache a SkPicture for
   // raster rather than directly using the display items.
   bool use_cached_picture_raster = true;
 
   LayerTreeDebugState initial_debug_state;
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_SETTINGS_H_