Register a separate default ui::EventTarget for Aura (Ash) to ensure that it does not interfere wit…

Register a separate default ui::EventTarget for Aura (Ash) to ensure that it does not interfere with the
event handling in desktop chrome in Aura. 

On Windows 8 in chrome metro mode we have a desktop chrome process
which runs as a server to the viewer process in Metro. Reusing the default EventTarget across both environments
causes desktop chrome to crash as a number of EventFilters registered on the default EventTarget get called twice.

The Ash specific EventTarget is implemented by the Ash::Shell class. The RootWindow in its GetParentTarget implementation
delegates this call to the EventClient implementation if one exists and if not it returns the default Aura::Env interface.

The EventClient interface is implemented by Ash and has been updated to return the default EventTarget via the new method
GetToplevelEventTarget

Fixes bug http://code.google.com/p/chromium/issues/detail?id=158105

BUG=158105
R=ben
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=164703

[Ben Goodger (Google), 2012-10-26 21:51:57]

https://codereview.chromium.org/11314013/diff/1/ui/aura/root_window.cc
File ui/aura/root_window.cc (right):

https://codereview.chromium.org/11314013/diff/1/ui/aura/root_window.cc#newcod...
ui/aura/root_window.cc:489: if (parent_event_target_)
instead of doing this can we add a method to ui/aura/client/event_client.h's
EventClient interface:

virtual ui::EventTarget* GetToplevelEventTarget() = 0;

and implement in ash/wm/event_client_impl.cc to return Shell::GetInstance();

This code then becomes:

return client::GetEventClient(this) ?
client::GetEventClient(this)->GetParentEventTarget() : Env::GetInstance();

and we can avoid adding state to the root window.

[ananta, 2012-10-26 22:28:41]

https://codereview.chromium.org/11314013/diff/1/ui/aura/root_window.cc
File ui/aura/root_window.cc (right):

https://codereview.chromium.org/11314013/diff/1/ui/aura/root_window.cc#newcod...
ui/aura/root_window.cc:489: if (parent_event_target_)
On 2012/10/26 21:51:57, Ben Goodger (Google) wrote:
> instead of doing this can we add a method to ui/aura/client/event_client.h's
> EventClient interface:
> 
> virtual ui::EventTarget* GetToplevelEventTarget() = 0;
> 
> and implement in ash/wm/event_client_impl.cc to return Shell::GetInstance();
> 
> This code then becomes:
> 
> return client::GetEventClient(this) ?
> client::GetEventClient(this)->GetParentEventTarget() : Env::GetInstance();
> 
> and we can avoid adding state to the root window.

Done.

[Ben Goodger (Google), 2012-10-28 04:24:20]

lgtm

https://codereview.chromium.org/11314013/diff/7004/ash/shell.h
File ash/shell.h (right):

https://codereview.chromium.org/11314013/diff/7004/ash/shell.h#newcode197
ash/shell.h:197: // Overridden from ui::EventTarget:
move these to be the last functions in the private section, and be sure to move
the implementations in the .cc too.