athena: Improve the overview mode support for split-view mode.

athena: Improve the overview mode support for split-view mode.

The notable changes:
. Do not allow horizontal dragging of the split windows.
. Do not show the 'Split' button when dragging a non-split window. Instead,
  highlight the split windows as drop targets.
. When a window is dropped on top of a left/right split window, switch to that
  window in that part of the split.

BUG=404119
R=oshima@chromium.org

Committed: https://chromium.googlesource.com/chromium/src/+/ab2250a2888e5483aaf2fe87ffb39154fa656d56

[sadrul, 2014-09-03 19:23:44]

sadrul@chromium.org changed reviewers:
+ oshima@chromium.org

[sadrul, 2014-09-03 19:24:45]

PS: There currently aren't any tests yet since we are still not sure what
behaviour we would actually want.

[oshima, 2014-09-03 20:02:59]

https://codereview.chromium.org/537073002/diff/1/athena/wm/window_overview_mo...
File athena/wm/window_overview_mode.cc (right):

https://codereview.chromium.org/537073002/diff/1/athena/wm/window_overview_mo...
athena/wm/window_overview_mode.cc:370: aura::Window*
IsSplitWindowDropTarget(const ui::GestureEvent& event) const {
Can this really be const?
(split_view_controller_->left_window() isn't const)

also I prefer to call it GetXxx if it returns aura::Window.

https://codereview.chromium.org/537073002/diff/1/athena/wm/window_overview_mo...
athena/wm/window_overview_mode.cc:612: dragged_window_ = NULL;
does this mean I cannot close the window in split view mode?
shouldn't we exit the split view if one of left/right window is closed instead?

[sadrul, 2014-09-03 20:14:27]

https://codereview.chromium.org/537073002/diff/1/athena/wm/window_overview_mo...
File athena/wm/window_overview_mode.cc (right):

https://codereview.chromium.org/537073002/diff/1/athena/wm/window_overview_mo...
athena/wm/window_overview_mode.cc:370: aura::Window*
IsSplitWindowDropTarget(const ui::GestureEvent& event) const {
On 2014/09/03 20:02:58, oshima wrote:
> Can this really be const?
> (split_view_controller_->left_window() isn't const)

The compiler doesn't seem to complain. (I can remove it though if you want. I
added it for readability)

> 
> also I prefer to call it GetXxx if it returns aura::Window.

Renamed to GetSplitWindowDropTarget().

https://codereview.chromium.org/537073002/diff/1/athena/wm/window_overview_mo...
athena/wm/window_overview_mode.cc:612: dragged_window_ = NULL;
On 2014/09/03 20:02:58, oshima wrote:
> does this mean I cannot close the window in split view mode?
> shouldn't we exit the split view if one of left/right window is closed
instead?

Yes. I am going to do that in the next patch. I have added a TODO comment here
explaining the rationale for now.

[oshima, 2014-09-03 20:53:48]

lgtm

https://codereview.chromium.org/537073002/diff/1/athena/wm/window_overview_mo...
File athena/wm/window_overview_mode.cc (right):

https://codereview.chromium.org/537073002/diff/1/athena/wm/window_overview_mo...
athena/wm/window_overview_mode.cc:370: aura::Window*
IsSplitWindowDropTarget(const ui::GestureEvent& event) const {
On 2014/09/03 20:14:27, sadrul wrote:
> On 2014/09/03 20:02:58, oshima wrote:
> > Can this really be const?
> > (split_view_controller_->left_window() isn't const)
> 
> The compiler doesn't seem to complain. (I can remove it though if you want. I
> added it for readability)

I'm actually onthe fence as split_view_controller isn't really owned by this
object.
I'm fine to leave it as is.

 
> > 
> > also I prefer to call it GetXxx if it returns aura::Window.
> 
> Renamed to GetSplitWindowDropTarget().

[sadrul, 2014-09-03 21:46:02]

Committed patchset #2 (id:20001) manually as ab2250a (presubmit successful).

[commit-bot: I haz the power, 2014-09-10 03:27:58]

Patchset 2 (id:??) landed as
https://crrev.com/ab2250a2888e5483aaf2fe87ffb39154fa656d56
Cr-Commit-Position: refs/heads/master@{#293202}