Update from https://crrev.com/307330

cc/trees/layer_tree_host.cc

 // 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.
 
 #include "cc/trees/layer_tree_host.h"
 
 #include <algorithm>
 #include <stack>
 #include <string>
 
@@ skipping 345 matching lines @@
         outer_viewport_scroll_layer_.get() ? outer_viewport_scroll_layer_->id()
                                            : Layer::INVALID_ID);
   } else {
     sync_tree->ClearViewportLayers();
   }
 
   sync_tree->RegisterSelection(selection_start_, selection_end_);
 
   sync_tree->PushPageScaleFromMainThread(
       page_scale_factor_, min_page_scale_factor_, max_page_scale_factor_);
+  sync_tree->elastic_overscroll()->PushFromMainThread(elastic_overscroll_);
+  if (sync_tree->IsActiveTree())
+    sync_tree->elastic_overscroll()->PushPendingToActive();
 
   sync_tree->PassSwapPromises(&swap_promise_list_);
 
   // Track the change in top controls height to offset the top_controls_delta
   // properly.  This is so that the top controls offset will be maintained
   // across height changes.
   float top_controls_height_delta =
       sync_tree->top_controls_height() - top_controls_height_;
 
   sync_tree->set_top_controls_shrink_blink_size(
@@ skipping 492 matching lines @@
 
     TRACE_EVENT0("cc", "LayerTreeHost::UpdateLayers::CalcDrawProps");
     bool can_render_to_separate_surface = true;
     // TODO(vmpstr): Passing 0 as the current render surface layer list id means
     // that we won't be able to detect if a layer is part of |update_list|.
     // Change this if this information is required.
     int render_surface_layer_list_id = 0;
     LayerTreeHostCommon::CalcDrawPropsMainInputs inputs(
         root_layer, device_viewport_size(), gfx::Transform(),
         device_scale_factor_, page_scale_factor_, page_scale_layer,
+        elastic_overscroll_, overscroll_elasticity_layer_.get(),
         GetRendererCapabilities().max_texture_size, settings_.can_use_lcd_text,
         settings_.layers_always_allowed_lcd_text,
         can_render_to_separate_surface,
         settings_.layer_transforms_should_scale_layer_contents, &update_list,
         render_surface_layer_list_id);
     LayerTreeHostCommon::CalculateDrawProperties(&inputs);
 
     if (total_frames_used_for_lcd_text_metrics_ <=
         kTotalFramesToUseForLCDTextMetrics) {
       LayerTreeHostCommon::CallFunctionForSubtree(
@@ skipping 231 matching lines @@
         inner_viewport_scroll_delta += info->scrolls[i].scroll_delta;
       } else {
         layer->SetScrollOffsetFromImplSide(
             gfx::ScrollOffsetWithDelta(layer->scroll_offset(),
                                        info->scrolls[i].scroll_delta));
       }
     }
   }
 
   if (!inner_viewport_scroll_delta.IsZero() ||
-      !outer_viewport_scroll_delta.IsZero() ||
-      info->page_scale_delta != 1.f ||
-      info->top_controls_delta) {
+      !outer_viewport_scroll_delta.IsZero() || info->page_scale_delta != 1.f ||
+      !info->elastic_overscroll_delta.IsZero() || info->top_controls_delta) {
     // Preemptively apply the scroll offset and scale delta here before sending
     // it to the client.  If the client comes back and sets it to the same
     // value, then the layer can early out without needing a full commit.
     if (inner_viewport_scroll_layer_.get()) {
       inner_viewport_scroll_layer_->SetScrollOffsetFromImplSide(
           gfx::ScrollOffsetWithDelta(
               inner_viewport_scroll_layer_->scroll_offset(),
               inner_viewport_scroll_delta));
     }
 
     if (outer_viewport_scroll_layer_.get()) {
       outer_viewport_scroll_layer_->SetScrollOffsetFromImplSide(
           gfx::ScrollOffsetWithDelta(
               outer_viewport_scroll_layer_->scroll_offset(),
               outer_viewport_scroll_delta));
     }
 
     ApplyPageScaleDeltaFromImplSide(info->page_scale_delta);
+    elastic_overscroll_ += info->elastic_overscroll_delta;
     if (!settings_.use_pinch_virtual_viewport) {
       client_->ApplyViewportDeltas(
           inner_viewport_scroll_delta + outer_viewport_scroll_delta,
           info->page_scale_delta,
           info->top_controls_delta);
     } else {
+      // TODO(ccameron): pass the elastic overscroll here so that input events
+      // may be translated appropriately.
       client_->ApplyViewportDeltas(
           inner_viewport_scroll_delta,
           outer_viewport_scroll_delta,
           info->page_scale_delta,
           info->top_controls_delta);
     }
   }
 }
 
 void LayerTreeHost::StartRateLimiter() {
@@ skipping 220 matching lines @@
     bool children_need_begin_frames) const {
   proxy_->SetChildrenNeedBeginFrames(children_need_begin_frames);
 }
 
 void LayerTreeHost::SendBeginFramesToChildren(
     const BeginFrameArgs& args) const {
   client_->SendBeginFramesToChildren(args);
 }
 
 }  // namespace cc