Accessibility manager shouldn't try to access ash Shelf from login screen.

chrome/browser/chromeos/accessibility/accessibility_manager.cc

Index: chrome/browser/chromeos/accessibility/accessibility_manager.cc
diff --git a/chrome/browser/chromeos/accessibility/accessibility_manager.cc b/chrome/browser/chromeos/accessibility/accessibility_manager.cc
index cdf37a793117fb182481dafa6f2c0c9d0ecefed3..1d0c9ab31304df829b08aaa6afbdd9889f46d655 100644
--- a/chrome/browser/chromeos/accessibility/accessibility_manager.cc
+++ b/chrome/browser/chromeos/accessibility/accessibility_manager.cc
@@ -365,6 +365,11 @@ void AccessibilityManager::PrefHandler::HandleProfileChanged(
     PrefService* user_prefs = current_profile->GetPrefs();
     user_prefs->Set(pref_path_, *value_on_login);
   }
+
+  // Update the panel height in the shelf layout manager when the profile
+  // changes, since the shelf layout manager doesn't exist in the login profile.
+  if (g_accessibility_manager)
+    g_accessibility_manager->UpdateChromeVoxPanelHeight();

[xiyuan, 2016/03/28 22:35:56]

Do this in AccessibilityManager::SetProfile so that we only do it once per
profile change?

[dmazzoni, 2016/03/29 20:43:22]

Done.

 }
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -1426,9 +1431,14 @@ void AccessibilityManager::OnChromeVoxPanelClosing() {
   aura::Window* root_window = chromevox_panel_->GetRootWindow();
   chromevox_panel_widget_observer_.reset(nullptr);
   chromevox_panel_ = nullptr;
-  ash::Shelf::ForWindow(root_window)
-      ->shelf_layout_manager()
-      ->SetChromeVoxPanelHeight(0);
+
+  ash::Shelf* shelf = ash::Shelf::ForWindow(root_window);
+  if (!shelf)
+    return;
+
+  ash::ShelfLayoutManager* shelf_layout_manager = shelf->shelf_layout_manager();
+  if (shelf_layout_manager)
+    shelf_layout_manager->SetChromeVoxPanelHeight(0);
 }
 
 void AccessibilityManager::OnChromeVoxPanelDestroying() {
@@ -1436,6 +1446,11 @@ void AccessibilityManager::OnChromeVoxPanelDestroying() {
   chromevox_panel_ = nullptr;
 }
 
+void AccessibilityManager::UpdateChromeVoxPanelHeight() {
+  if (chromevox_panel_)
+    chromevox_panel_->UpdatePanelHeight();
+}
+
 void AccessibilityManager::SetKeyboardListenerExtensionId(
     const std::string& id,
     content::BrowserContext* context) {