Implement overscroll support for the virtual keyboard.

content/browser/renderer_host/render_widget_host_impl.cc

Index: content/browser/renderer_host/render_widget_host_impl.cc
diff --git a/content/browser/renderer_host/render_widget_host_impl.cc b/content/browser/renderer_host/render_widget_host_impl.cc
index 2b3762f9a3c8318bea87c7e8be08e2da428b8975..45a12bebe56e01609c66949084bc8a8757f9fb10 100644
--- a/content/browser/renderer_host/render_widget_host_impl.cc
+++ b/content/browser/renderer_host/render_widget_host_impl.cc
@@ -601,13 +601,16 @@ void RenderWidgetHostImpl::WasResized() {
   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;
@@ -627,6 +630,7 @@ void RenderWidgetHostImpl::WasResized() {
   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))) {