Make tile size a function of the device scale factor.

cc/trees/layer_tree_settings_unittest.cc

Index: cc/trees/layer_tree_settings_unittest.cc
diff --git a/cc/trees/layer_tree_settings_unittest.cc b/cc/trees/layer_tree_settings_unittest.cc
index f406a90598860eabe030750901cd30ee2d7b933b..2a6a61f12af75558ac430f58c3e31f018127f69c 100644
--- a/cc/trees/layer_tree_settings_unittest.cc
+++ b/cc/trees/layer_tree_settings_unittest.cc
@@ -64,8 +64,7 @@ TEST(LayerTreeSettingsTest, AllMembersChanged) {
   settings.top_controls_show_threshold = 0.44f;
   settings.top_controls_hide_threshold = 0.45f;
   settings.background_animation_rate = 0.46f;
-  settings.default_tile_size = gfx::Size(47, 48);
-  settings.max_untiled_layer_size = gfx::Size(49, 50);
+  settings.use_viewport_for_tile_size = !settings.use_viewport_for_tile_size;
   settings.minimum_occlusion_tracking_size = gfx::Size(51, 52);
   settings.tiling_interest_area_padding =
       settings.tiling_interest_area_padding * 3 + 1;
@@ -125,8 +124,7 @@ TEST(LayerTreeSettingsTest, ArbitraryValues) {
   settings.top_controls_hide_threshold = 0.666f;
   settings.top_controls_hide_threshold = 0.51f;
   settings.background_animation_rate = 0.52f;
-  settings.default_tile_size = gfx::Size(53, 54);
-  settings.max_untiled_layer_size = gfx::Size(55, 56);
+  settings.use_viewport_for_tile_size = true;
   settings.minimum_occlusion_tracking_size = gfx::Size(57, 58);
   settings.tiling_interest_area_padding = 59;
   settings.skewport_target_time_in_seconds = 0.6f;