Add WM_EVENT_TRUSTED_PIN and WINDOW_STATE_TYPE_TRUSTED_PINNED to Ash.

ash/accelerators/accelerator_controller_delegate_aura.cc

Index: ash/accelerators/accelerator_controller_delegate_aura.cc
diff --git a/ash/accelerators/accelerator_controller_delegate_aura.cc b/ash/accelerators/accelerator_controller_delegate_aura.cc
index 654edd57b44a4a8ebadda05b631ca00f2ec11d44..0a9c88f5fcd39aa23f6d627933ccf8df6181f7fa 100644
--- a/ash/accelerators/accelerator_controller_delegate_aura.cc
+++ b/ash/accelerators/accelerator_controller_delegate_aura.cc
@@ -314,8 +314,11 @@ void HandleToggleDesktopBackgroundMode() {
 }
 
 bool CanHandleUnpin() {

[hidehiko, 2016/08/29 14:31:38]

Looks to work practically, but is it ok to leave UNPIN in the table?
https://cs.chromium.org/chromium/src/ash/common/accelerators/accelerator_tabl...

[hirono, 2016/08/30 07:16:08]

I tried to create a new list in accelerator_table.cc for trusted pin state 
after getting the comment. But now I feel like keeping the implementation as it
it.

The accelerator action list is referred by accelerator controller. And
accelerator controller accesses wm::Shell to get current shell state. However 
wm::Shell does not know the difference between trusted pinned and normal pinned,
which I'd like to keep hiding internally.

WDYT?

+  // Returns true only for WINDOW_STATE_TYPE_PINNED.
+  // WINDOW_STATE_TYPE_TRUSTED_PINNED does not accept user's unpin operation.
   wm::WindowState* window_state = wm::GetActiveWindowState();
-  return window_state && window_state->IsPinned();
+  return window_state &&
+         window_state->GetStateType() == wm::WINDOW_STATE_TYPE_PINNED;
 }
 
 #if defined(OS_CHROMEOS)