Don't reset scroll position of contents on every ScrollView layout.

ui/views/controls/scroll_view.cc

 // Copyright (c) 2012 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 "ui/views/controls/scroll_view.h"
 
 #include "base/feature_list.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "ui/events/event.h"
@@ skipping 295 matching lines @@
     focus_ring_->Layout();
 
   gfx::Rect available_rect = GetContentsBounds();
   if (is_bounded()) {
     int content_width = available_rect.width();
     int content_height = contents()->GetHeightForWidth(content_width);
     if (content_height > height()) {
       content_width = std::max(content_width - GetScrollBarWidth(), 0);
       content_height = contents()->GetHeightForWidth(content_width);
     }
-    if (contents()->bounds().size() != gfx::Size(content_width, content_height))
-      contents()->SetBounds(0, 0, content_width, content_height);
+    contents()->SetSize(gfx::Size(content_width, content_height));

[sky, 2016/11/16 20:12:57]

It would be nice if we were consistent and used contents_ and not contents(). I
think it's this block that uses contents() rahter than contents_.

[Evan Stade, 2016/11/17 01:14:00]

(also done)

   }
 
   // Most views will want to auto-fit the available space. Most of them want to
   // use all available width (without overflowing) and only overflow in
   // height. Examples are HistoryView, MostVisitedView, DownloadTabView, etc.
   // Other views want to fit in both ways. An example is PrintView. To make both
   // happy, assume a vertical scrollbar but no horizontal scrollbar. To override
   // this default behavior, the inner view has to calculate the available space,
   // used ComputeScrollBarsVisibility() to use the same calculation that is done
   // here and sets its bound to fit within.
@@ skipping 454 matching lines @@
 
 VariableRowHeightScrollHelper::RowInfo
     FixedRowHeightScrollHelper::GetRowInfo(int y) {
   if (y < top_margin_)
     return RowInfo(0, top_margin_);
   return RowInfo((y - top_margin_) / row_height_ * row_height_ + top_margin_,
                  row_height_);
 }
 
 }  // namespace views