Enables storing shelf's auto_hide_behavior and alignment per display.

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
diff --git a/chrome/common/pref_names.cc b/chrome/common/pref_names.cc
index b7945dbf854803dce7bd88d43e78365214d71436..ab713ed36611b8cc68629f1ae13c0662669765b6 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -2091,6 +2091,8 @@ const char kMediaGalleriesRememberedGalleries[] =
 // set its value is set from the synced value (once prefs have been
 // synced). This gives a per-machine setting that is initialized from the last
 // set value.
+// These values are default on the machine but can be overridden by per-display
+// values in kShelfPreferences (unless overridden by managed policy).
 // String value corresponding to ash::Shell::ShelfAlignment.
 const char kShelfAlignment[] = "shelf_alignment";
 const char kShelfAlignmentLocal[] = "shelf_alignment_local";
@@ -2100,6 +2102,11 @@ const char kShelfAutoHideBehaviorLocal[] = "auto_hide_behavior_local";
 const char kPinnedLauncherApps[] = "pinned_launcher_apps";
 // Boolean value indicating whether to show a logout button in the ash tray.
 const char kShowLogoutButtonInTray[] = "show_logout_button_in_tray";
+// Dictionary value that holds per-display preference of shelf alignment and
+// auto-hide behavior. Key of the dictionary is the id of the display, and
+// its value is a dictionary whose keys are kShelfAlignment and
+// kShelfAutoHideBehavior.
+const char kShelfPreferences[] = "shelf_preferences";
 
 const char kFlingVelocityCap[] = "gesture.fling_velocity_cap";
 const char kLongPressTimeInSeconds[] =