Introduce WindowStateDelegate::ToggleFullscreen

ash/accelerators/accelerator_commands.h

Index: ash/accelerators/accelerator_commands.h
diff --git a/ash/accelerators/accelerator_commands.h b/ash/accelerators/accelerator_commands.h
index 36006e7ebede569ef092457fd92d14bdf1fb86a0..90df49e7284cdb4c19fa3317b8186bf4469b9b33 100644
--- a/ash/accelerators/accelerator_commands.h
+++ b/ash/accelerators/accelerator_commands.h
@@ -9,6 +9,7 @@
 
 // This file contains implementations of commands that are bound to keyboard
 // shortcuts in Ash or in the embedding application (e.g. Chrome).
+// Note about tests:
 namespace ash {
 namespace accelerators {
 
@@ -21,6 +22,10 @@ ASH_EXPORT bool ToggleMinimized();
 // fullscreen mode.
 ASH_EXPORT void ToggleMaximized();
 
+// Toggles the fullscreen state. The behavior can be overridden
+// by WindowStateDelegate::ToggleFullscreen().
+ASH_EXPORT void ToggleFullscreen();
+
 }  // namespace accelerators
 }  // namespace ash