Purge the ScrollBlocksOn code.

cc/proto/layer.proto

 // 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 "display_list_recording_source.proto";
 import "layer_position_constraint.proto";
 import "point3f.proto";
 import "pointf.proto";
@@ skipping 74 matching lines @@
   optional bool has_render_surface = 11;
   // TODO(nyquist): Add support for FilterOperation. See crbug.com/541321.
   // repeated FilterOperation filters = 12;
   // repeated FilterOperation background_filters = 13;
   optional bool masks_to_bounds = 14;
   optional uint32 main_thread_scrolling_reasons = 15;
   optional bool have_wheel_event_handlers = 16;
   optional bool have_scroll_event_handlers = 17;
   optional Region non_fast_scrollable_region = 18;
   optional Region touch_event_handler_region = 19;
-  optional int32 scroll_blocks_on = 20;
   optional bool contents_opaque = 21;
   optional float opacity = 22;
   optional SkXfermode.Mode blend_mode = 23;
   optional bool is_root_for_isolated_group = 24;
   optional PointF position = 25;
   optional bool is_container_for_fixed_position_layers = 26;
   optional LayerPositionConstraint position_constraint = 27;
   optional bool should_flatten_transform = 28;
   optional bool should_flatten_transform_from_property_tree = 29;
   optional int32 num_layer_or_descendants_with_copy_request = 30;
@@ skipping 29 matching lines @@
 
 message PictureLayerProperties {
   optional DisplayListRecordingSource recording_source = 1;
   optional Region invalidation = 2;
   optional Rect last_updated_visible_layer_rect = 3;
   optional bool is_mask = 4;
   optional bool nearest_neighbor = 5;
 
   optional int64 update_source_frame_number = 6;
 }