Add support for LayerTreeSettings (de)serialization

cc/proto/layer_tree_settings.proto

Index: cc/proto/layer_tree_settings.proto
diff --git a/cc/proto/layer_tree_settings.proto b/cc/proto/layer_tree_settings.proto
new file mode 100644
index 0000000000000000000000000000000000000000..1c0bb8538796089e966c779b060a04a9745e4a87
--- /dev/null
+++ b/cc/proto/layer_tree_settings.proto
@@ -0,0 +1,73 @@
+// Copyright 2015 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.
+
+syntax = "proto2";
+
+import "layer_tree_debug_state.proto";
+import "managed_memory_policy.proto";
+import "renderer_settings.proto";
+import "size.proto";
+
+package cc.proto;
+
+option optimize_for = LITE_RUNTIME;
+
+message LayerTreeSettings {
+  enum ScrollbarAnimator {
+    UNKNOWN = 0;
+    NO_ANIMATOR = 1;
+    LINEAR_FADE = 2;
+    THINNING = 3;
+  };
+
+  optional RendererSettings renderer_settings = 1;
+  optional bool single_thread_proxy_scheduler = 2;
+  optional bool use_external_begin_frame_source = 3;
+  optional bool main_frame_before_activation_enabled = 4;
+  optional bool using_synchronous_renderer_compositor = 5;
+  optional bool accelerated_animation_enabled = 6;
+  optional bool can_use_lcd_text = 7;
+  optional bool use_distance_field_text = 8;
+  optional bool gpu_rasterization_enabled = 9;
+  optional bool gpu_rasterization_forced = 10;
+  optional int32 gpu_rasterization_msaa_sample_count = 11;
+  optional float gpu_rasterization_skewport_target_time_in_seconds = 12;
+  optional bool create_low_res_tiling = 13;
+  optional ScrollbarAnimator scrollbar_animator = 14;
+  optional int32 scrollbar_fade_delay_ms = 15;
+  optional int32 scrollbar_fade_resize_delay_ms = 16;
+  optional int32 scrollbar_fade_duration_ms = 17;
+  optional uint32 solid_color_scrollbar_color = 18; /* SkColor */
+  optional bool timeout_and_draw_when_animation_checkerboards = 19;
+  optional bool layer_transforms_should_scale_layer_contents = 20;
+  optional bool layers_always_allowed_lcd_text = 21;
+  optional float minimum_contents_scale = 22;
+  optional float low_res_contents_scale_factor = 23;
+  optional float top_controls_show_threshold = 24;
+  optional float top_controls_hide_threshold = 25;
+  optional double background_animation_rate = 26;
+  optional Size default_tile_size = 27;
+  optional Size max_untiled_layer_size = 28;
+  optional Size minimum_occlusion_tracking_size = 29;
+  optional uint32 tiling_interest_area_padding = 30;
+  optional float skewport_target_time_in_seconds = 31;
+  optional int32 skewport_extrapolation_limit_in_content_pixels = 32;
+  optional uint32 max_memory_for_prepaint_percentage = 33;
+  optional bool strict_layer_property_change_checking = 34;
+  optional bool use_zero_copy = 35;
+  optional bool use_partial_raster = 36;
+  optional bool enable_elastic_overscroll = 37;
+  repeated uint32 use_image_texture_targets = 38;
+  optional bool ignore_root_layer_flings = 39;
+  optional uint32 scheduled_raster_task_limit = 40;
+  optional bool use_occlusion_for_tile_prioritization = 41;
+  optional bool verify_property_trees = 42;
+  optional bool use_property_trees = 43;
+  optional bool image_decode_tasks_enabled = 44;
+  optional bool use_compositor_animation_timelines = 45;
+  optional bool wait_for_beginframe_interval = 46;
+  optional int32 max_staging_buffer_usage_in_bytes = 47;
+  optional ManagedMemoryPolicy memory_policy = 48;
+  optional LayerTreeDebugState initial_debug_state = 49;
+}