Whitelist Java ToS-accepted pref for backup & restore.

This is needed for to correctly enabled variations seed
fetching after backup & restore in conjunction with this
CL: https://codereview.chromium.org/2614183002

BUG=669543

Review-Url: https://codereview.chromium.org/2621413008
Cr-Commit-Position: refs/heads/master@{#443373}

chrome/android/java/src/org/chromium/chrome/browser/ChromeBackupAgent.java

@@ -17,6 +17,7 @@ import org.chromium.base.ThreadUtils;
 import org.chromium.base.VisibleForTesting;
 import org.chromium.base.annotations.SuppressFBWarnings;
 import org.chromium.base.library_loader.ProcessInitException;
+import org.chromium.chrome.browser.firstrun.FirstRunGlueImpl;
 import org.chromium.chrome.browser.firstrun.FirstRunSignInProcessor;
 import org.chromium.chrome.browser.firstrun.FirstRunStatus;
 import org.chromium.chrome.browser.init.ChromeBrowserInitializer;
@@ -46,6 +47,7 @@ public class ChromeBackupAgent extends BackupAgent {
     // Lists of preferences that should be restored unchanged.
 
     static final String[] BACKUP_ANDROID_BOOL_PREFS = {
+            FirstRunGlueImpl.CACHED_TOS_ACCEPTED_PREF,
             FirstRunStatus.FIRST_RUN_FLOW_COMPLETE,
             FirstRunStatus.LIGHTWEIGHT_FIRST_RUN_FLOW_COMPLETE,
             FirstRunSignInProcessor.FIRST_RUN_FLOW_SIGNIN_SETUP,

chrome/android/java/src/org/chromium/chrome/browser/firstrun/FirstRunGlueImpl.java

@@ -21,7 +21,7 @@ import java.util.List;
  * Provides preferences glue for FirstRunActivity.
  */
 public class FirstRunGlueImpl implements FirstRunGlue {
-    private static final String CACHED_TOS_ACCEPTED_PREF = "first_run_tos_accepted";
+    public static final String CACHED_TOS_ACCEPTED_PREF = "first_run_tos_accepted";
 
     /**
      * Synchronizes first run native and Java preferences.