Center the focus of the text input in magnifier screen.

ash/magnifier/magnification_controller.h

Index: ash/magnifier/magnification_controller.h
diff --git a/ash/magnifier/magnification_controller.h b/ash/magnifier/magnification_controller.h
index 319989be2b10f3d32984abb6c0cedee1fe7488c5..51816168b507e5379e3f4cfd358fe3163527f937 100644
--- a/ash/magnifier/magnification_controller.h
+++ b/ash/magnifier/magnification_controller.h
@@ -40,6 +40,13 @@ class ASH_EXPORT MagnificationController {
   // Returns if the screen magnifier is enabled or not.
   virtual bool IsEnabled() const = 0;
 
+  // Enables or disables the feature for keeping the text input focus centered.
+  virtual void SetKeepFocusCentered(bool keep_focus_centered) = 0;
+
+  // Returns true if magnifier will keep the focus centered in screen for text
+  // input.
+  virtual bool KeepFocusCentered() const = 0;
+
   // Sets the magnification ratio. 1.0f means no magnification.
   virtual void SetScale(float scale, bool animate) = 0;
   // Returns the current magnification ratio.