Enables storing shelf's auto_hide_behavior and alignment per display.

ash/shell.cc

Index: ash/shell.cc
diff --git a/ash/shell.cc b/ash/shell.cc
index 0d4461c6a4f5810fda0a5940469fe0cb42bed08d..5ec2435b2f5f20b2a8b0de8547b1704e259cc9f1 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -718,8 +718,10 @@ ShelfAutoHideBehavior Shell::GetShelfAutoHideBehavior(
 
 void Shell::SetShelfAlignment(ShelfAlignment alignment,
                               aura::RootWindow* root_window) {
-  if (GetRootWindowController(root_window)->SetShelfAlignment(alignment))
-    FOR_EACH_OBSERVER(ShellObserver, observers_, OnShelfAlignmentChanged());
+  if (GetRootWindowController(root_window)->SetShelfAlignment(alignment)) {
+    FOR_EACH_OBSERVER(
+        ShellObserver, observers_, OnShelfAlignmentChanged(root_window));
+  }
 }
 
 ShelfAlignment Shell::GetShelfAlignment(aura::RootWindow* root_window) {