[Sync] Restore previous session if no tabbed windows present

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

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chrome.browser;
 
 import android.graphics.Color;
 import android.os.Build;
 import android.os.Handler;
 import android.util.Log;
 import android.util.Pair;
 
 import org.chromium.base.StreamUtil;
 import org.chromium.base.VisibleForTesting;
 import org.chromium.chrome.browser.tab.Tab;
+import org.chromium.components.sync.SyncConstants;
 import org.chromium.content.browser.crypto.CipherFactory;
 import org.chromium.content_public.browser.WebContents;
 
 import java.io.DataInputStream;
 import java.io.DataOutputStream;
 import java.io.EOFException;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
@@ skipping 223 matching lines @@
                 tabState.contentsState.setVersion(isStableChannelBuild() ? 0 : 1);
 
                 // Could happen if reading a version of a TabState that does not include the
                 // version id.
                 Log.w(TAG, "Failed to read saved state version id from tab state. Assuming "
                         + "version " + tabState.contentsState.version());
             }
             try {
                 tabState.syncId = stream.readLong();
             } catch (EOFException eof) {
-                tabState.syncId = 0;
+                tabState.syncId = SyncConstants.INVALID_TAB_NODE_ID;
                 // Could happen if reading a version of TabState without syncId.
-                Log.w(TAG, "Failed to read syncId from tab state. Assuming syncId is: 0");
+                Log.w(TAG, "Failed to read syncId from tab state. Assuming syncId is: -1");
             }
             try {
                 tabState.shouldPreserve = stream.readBoolean();
             } catch (EOFException eof) {
                 // Could happen if reading a version of TabState without this flag set.
                 tabState.shouldPreserve = false;
                 Log.w(TAG, "Failed to read shouldPreserve flag from tab state. "
                         + "Assuming shouldPreserve is false");
             }
             tabState.mIsIncognito = encrypted;
@@ skipping 205 matching lines @@
 
     private static native String nativeGetDisplayTitleFromByteBuffer(
             ByteBuffer state, int savedStateVersion);
 
     private static native String nativeGetVirtualUrlFromByteBuffer(
             ByteBuffer state, int savedStateVersion);
 
     private static native void nativeFreeWebContentsStateBuffer(ByteBuffer buffer);
 
     private static native void nativeCreateHistoricalTab(ByteBuffer state, int savedStateVersion);
-}
+}