Created the dialog offering the user to merge their account data or keep it

chrome/android/java/src/org/chromium/chrome/browser/preferences/SyncedAccountPreference.java

Index: chrome/android/java/src/org/chromium/chrome/browser/preferences/SyncedAccountPreference.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/preferences/SyncedAccountPreference.java b/chrome/android/java/src/org/chromium/chrome/browser/preferences/SyncedAccountPreference.java
index 9a7f8ff9fe92613900b8c53c4bca72bec681b0fb..d182d6d60c838540cd0cf2f7d68dcbb58ae1c2ea 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/preferences/SyncedAccountPreference.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/preferences/SyncedAccountPreference.java
@@ -20,6 +20,7 @@ import org.chromium.sync.signin.ChromeSigninController;
  * account to use for syncing
  */
 public class SyncedAccountPreference extends ListPreference {
+    private static final String TAG = "SyncedAccountPreference";
 
     /**
      * Constructor for inflating from XML
@@ -30,6 +31,10 @@ public class SyncedAccountPreference extends ListPreference {
         updateAccountsList();
     }
 
+    public void update() {
+        updateAccountsList();
+    }
+
     private void updateAccountsList() {
         boolean syncEnabled = AndroidSyncSettings.isSyncEnabled(getContext());
         if (!syncEnabled) {
@@ -57,13 +62,19 @@ public class SyncedAccountPreference extends ListPreference {
 
         setEntries(accountNames);
         setEntryValues(accountValues);
-        setDefaultValue(signedInSettingsKey);
+        setValue(signedInSettingsKey);
         setSummary(signedInAccountName);
     }
 
+    public String valueToEntry(String value) {
+        // It is useful to have a way of mapping from values (the data the SyncedAccountPreference
+        // stores) to entries (the data displayed to the user). At the moment they are the same
+        // but this may change and it's neater to keep the logic in this class.
+        return value;
+    }
+
     @Override
     protected void onDialogClosed(boolean positiveResult) {
         super.onDialogClosed(positiveResult);
-        // TODO(crbug/557786): Add switching sync accounts
     }
 }