Handle UNPIN operation in ash.

ash/accelerators/accelerator_commands.cc

Index: ash/accelerators/accelerator_commands.cc
diff --git a/ash/accelerators/accelerator_commands.cc b/ash/accelerators/accelerator_commands.cc
index 94cc0566860e41e0fe8d14d668d3347c1ff8f4f8..2a6c9845dec5e8ca29bace0d55428f8aff06bd25 100644
--- a/ash/accelerators/accelerator_commands.cc
+++ b/ash/accelerators/accelerator_commands.cc
@@ -107,5 +107,11 @@ void ResetInternalDisplayZoom() {
   }
 }
 
+void Unpin() {
+  wm::WindowState* window_state = wm::GetActiveWindowState();

[oshima, 2016/06/18 09:48:22]

I think it's safer to get pinned window from ScreenPinningController.
It *should* be same, but active window can change even during pinned (system
modal, lock screen are example)

[hidehiko, 2016/06/18 10:02:23]

I see. Done.

+  if (window_state->IsPinned())
+    window_state->Restore();
+}
+
 }  // namespace accelerators
 }  // namespace ash