[not for review - epic CL] Adding Elastic+Momentum+Layered scrolling to views::ScrollView

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_item.proto";
 import "layer_position_constraint.proto";
 import "layer_sticky_position_constraint.proto";
 import "point3f.proto";
@@ skipping 52 matching lines @@
   // The Layer base class and each descendant have different proto messages
   // for their specific properties.
   optional BaseLayerProperties base = 5;
 
   // Only one of these fields may be set per LayerProperties.
   // TODO(dtrainor): use a 'oneof' union when it's supported in Chromium.  See
   // crbug.com/570371.
   optional PictureLayerProperties picture = 6;
 }
 
-// NEXT ID: 59
+// NEXT ID: 61
 message BaseLayerProperties {
   // The following fields mirror the data stored in Layer::Inputs ----------
   optional Rect update_rect = 46;
   optional Size bounds = 3;
   optional bool masks_to_bounds = 14;
   optional float opacity = 22;
   optional SkXfermode.Mode blend_mode = 23;
   optional bool is_root_for_isolated_group = 24;
   optional bool contents_opaque = 21;
   optional PointF position = 25;
   optional Transform transform = 33;
   optional Point3F transform_origin = 1;
   optional bool is_drawable = 56;
   optional bool double_sided = 8;
   optional bool should_flatten_transform = 28;
   optional int32 sorting_context_id = 35;
   optional bool use_parent_backface_visibility = 32;
   optional uint32 background_color = 2;
   // TODO(nyquist): Add support for FilterOperation. See crbug.com/541321.
   // repeated FilterOperation filters = 12;
   // repeated FilterOperation background_filters = 13;
   // optional PointF filters_origin = 57
   optional ScrollOffset scroll_offset = 44;
+  optional ScrollOffset overscroll = 59;
+  optional bool can_overscroll = 60;
   optional int32 scroll_clip_layer_id = 37;
   optional bool user_scrollable_horizontal = 38;
   optional bool user_scrollable_vertical = 39;
   optional uint32 main_thread_scrolling_reasons = 15;
 
   optional Region non_fast_scrollable_region = 18;
   // TODO(khushalsagar): Do we actually need these? Touch events are never sent
   // back to the engine.
   optional Region touch_event_handler_region = 19;
 
@@ skipping 61 matching lines @@
     HORIZONTAL = 0;
     VERTICAL = 1;
   };
 
   optional int32 scroll_layer_id = 1;
   optional int32 thumb_thickness = 2;
   optional int32 track_start = 3;
   optional bool is_left_side_vertical_scrollbar = 4;
   optional ScrollbarOrientation orientation = 5;
 }