Center the focus of the text input in magnifier screen.

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 c3b1f85dcf02136ca8504745f4d266f7885430d5..f9a56b34320b4940464aacb3762578eda948c217 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -566,6 +566,10 @@ const char kAccessibilityHighContrastEnabled[] =
 // A boolean pref which determines whether screen magnifier is enabled.
 const char kAccessibilityScreenMagnifierEnabled[] =
     "settings.a11y.screen_magnifier";
+// A boolean pref which determines whether screen magnifier should center
+// the text input focus.
+const char kAccessibilityScreenMagnifierCenterFocus[] =
+    "settings.a11y.screen_magnifier_center_focus";
 // A integer pref which determines what type of screen magnifier is enabled.
 // Note that: 'screen_magnifier_type' had been used as string pref. Hence,
 // we are using another name pref here.