Reflect fullscreen magnifier accelerator toggle in settings and tray

Currently, when ctrl+search+m is used to toggle the magnifier,
this is not reflected in chrome://settings.

However, the other accelerators (docked magnifier and high contrast)
are reflected in settings.

Bug: 853104
Test: Manual
Change-Id: Ia70b868eb89598ba90b79e2e5da482bd0bb6a916
Reviewed-on: https://chromium-review.googlesource.com/1114524
Commit-Queue: Sara Kato <sarakato@chromium.org>
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Reviewed-by: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572416}

ash/accelerators/accelerator_controller.cc

@@ -880,7 +880,13 @@ void SetFullscreenMagnifierEnabled(bool enabled) {
   } else {
     RemoveStickyNotitification(kFullscreenMagnifierToggleAccelNotificationId);
   }
-  Shell::Get()->magnification_controller()->SetEnabled(enabled);
+
+  // TODO (afakhry): Move the below into a single call (crbug/817157).
+  // Necessary to make magnification controller in ash observe changes to the
+  // prefs iteself.
+  Shell* shell = Shell::Get();
+  shell->accessibility_controller()->SetFullscreenMagnifierEnabled(enabled);
+  shell->magnification_controller()->SetEnabled(enabled);
 }
 
 void SetHighContrastEnabled(bool enabled) {

ash/accessibility/accessibility_controller.cc

@@ -426,6 +426,14 @@ bool AccessibilityController::IsFocusHighlightEnabled() const {
   return focus_highlight_enabled_;
 }
 
+void AccessibilityController::SetFullscreenMagnifierEnabled(bool enabled) {
+  if (!active_user_prefs_)
+    return;
+  active_user_prefs_->SetBoolean(prefs::kAccessibilityScreenMagnifierEnabled,
+                                 enabled);
+  active_user_prefs_->CommitPendingWrite();
+}
+
 void AccessibilityController::SetHighContrastEnabled(bool enabled) {
   if (!active_user_prefs_)
     return;

ash/accessibility/accessibility_controller.h

@@ -80,6 +80,8 @@ class ASH_EXPORT AccessibilityController
   void SetFocusHighlightEnabled(bool enabled);
   bool IsFocusHighlightEnabled() const;
 
+  void SetFullscreenMagnifierEnabled(bool enabled);
+
   void SetHighContrastEnabled(bool enabled);
   bool IsHighContrastEnabled() const;