[Sync] Restore previous session if no tabbed windows present

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

Index: chrome/android/java/src/org/chromium/chrome/browser/TabState.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/TabState.java b/chrome/android/java/src/org/chromium/chrome/browser/TabState.java
index 72824c006eeab6f5658f3fd6b66c8b0f8a895745..26e4ad2dc7f63c17f2f78126fbff132af5a805d0 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/TabState.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/TabState.java
@@ -256,9 +256,9 @@ public class TabState {
             try {
                 tabState.syncId = stream.readLong();
             } catch (EOFException eof) {
-                tabState.syncId = 0;
+                tabState.syncId = -1;

[skym, 2017/04/17 20:37:02]

Can we redefine an invalid sync id in java land that we can point back to C++
constant via a comment?

[Nicolas Zea, 2017/04/17 21:24:54]

Done.

                 // 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();
@@ -484,4 +484,4 @@ public class TabState {
     private static native void nativeFreeWebContentsStateBuffer(ByteBuffer buffer);
 
     private static native void nativeCreateHistoricalTab(ByteBuffer state, int savedStateVersion);
-}
+}