Implement overscroll support for the virtual keyboard.

content/browser/renderer_host/render_widget_host_impl.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 "content/browser/renderer_host/render_widget_host_impl.h"
 
 #include <math.h>
 #include <set>
 #include <utility>
 
@@ skipping 583 matching lines @@
 
   gfx::Rect view_bounds = view_->GetViewBounds();
   gfx::Size new_size(view_bounds.size());
 
   gfx::Size old_physical_backing_size = physical_backing_size_;
   physical_backing_size_ = view_->GetPhysicalBackingSize();
   bool was_fullscreen = is_fullscreen_;
   is_fullscreen_ = IsFullscreen();
   float old_overdraw_bottom_height = overdraw_bottom_height_;
   overdraw_bottom_height_ = view_->GetOverdrawBottomHeight();
+  int old_visible_viewport_height = visible_viewport_height_;
+  visible_viewport_height_ = view_->GetVisibleViewportHeight();
 
   bool size_changed = new_size != last_requested_size_;
   bool side_payload_changed =
       screen_info_out_of_date_ ||
       old_physical_backing_size != physical_backing_size_ ||
       was_fullscreen != is_fullscreen_ ||
-      old_overdraw_bottom_height != overdraw_bottom_height_;
+      old_overdraw_bottom_height != overdraw_bottom_height_ ||
+      old_visible_viewport_height != visible_viewport_height_;
 
   if (!size_changed && !side_payload_changed)
     return;
 
   if (!screen_info_) {
     screen_info_.reset(new blink::WebScreenInfo);
     GetWebScreenInfo(screen_info_.get());
   }
 
   // We don't expect to receive an ACK when the requested size or the physical
   // backing size is empty, or when the main viewport size didn't change.
   if (!new_size.IsEmpty() && !physical_backing_size_.IsEmpty() && size_changed)
     resize_ack_pending_ = g_check_for_pending_resize_ack;
 
   ViewMsg_Resize_Params params;
   params.screen_info = *screen_info_;
   params.new_size = new_size;
   params.physical_backing_size = physical_backing_size_;
   params.overdraw_bottom_height = overdraw_bottom_height_;

[kevers, 2014/04/23 17:09:13]

Based on discussions with aelias, it appears that overdraw_bottom_height may be
phased out for Android.  Introducing a new parameter to avoid complicating this
cleanup.

[aelias_OOO_until_Jul13, 2014/04/23 19:41:58]

Hmm, it's ugly to introduce a new parameter for such a similar purpose, but I've
racked my brain for 15 minutes and I don't see a way to use the same parameter
for all platforms owing to the completely different viewport models Android and
ChromeOS have chosen.  overdraw_bottom_height is a delta from
physical_backing_size (and must remain so for complicated reasons relating to
top controls), while visible_viewport_size is an absolute size in the same space
as "size_".  As you say, Android will be able to eventually get rid of
overdraw_bottom_height after some top controls refactorings come through, so I
guess we can duplicate it for now.

But I suggest making it gfx::SizeF visible_viewport_size -- Size because it's
silly to only be able to change the height and not the width, and F because it's
in DIP pixels and therefore fractional values may be needed to represent odd
numbers of physical pixels at dpi scale 2.  (I know the Blink API is in ints so
you can floor it at that time, but let's maintain precision until then.)

[kevers, 2014/04/24 02:02:13]

Done.

[kevers, 2014/04/24 18:38:33]

Using Size instead of SizeF based on sky's feedback.

+  params.visible_viewport_height = visible_viewport_height_;
   params.resizer_rect = GetRootWindowResizerRect();
   params.is_fullscreen = is_fullscreen_;
   if (!Send(new ViewMsg_Resize(routing_id_, params))) {
     resize_ack_pending_ = false;
   } else {
     last_requested_size_ = new_size;
   }
 }
 
 void RenderWidgetHostImpl::ResizeRectChanged(const gfx::Rect& new_rect) {
@@ skipping 1769 matching lines @@
   }
 }
 
 SkBitmap::Config RenderWidgetHostImpl::PreferredReadbackFormat() {
   if (view_)
     return view_->PreferredReadbackFormat();
   return SkBitmap::kARGB_8888_Config;
 }
 
 }  // namespace content