Fix buffer underflow bug in tab save state.

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 16150938f243e033b1017ec47b3131ae61148f4e..72824c006eeab6f5658f3fd6b66c8b0f8a895745 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/TabState.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/TabState.java
@@ -5,6 +5,7 @@
 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;
@@ -298,9 +299,18 @@ public class TabState {
         // Create the byte array from contentsState before opening the FileOutputStream, in case
         // contentsState.buffer is an instance of MappedByteBuffer that is mapped to
         // the tab state file.
-        state.contentsState.buffer().rewind();
-        byte[] contentsStateBytes = new byte[state.contentsState.buffer().remaining()];
-        state.contentsState.buffer().get(contentsStateBytes);
+        byte[] contentsStateBytes = new byte[state.contentsState.buffer().limit()];
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
+            state.contentsState.buffer().rewind();
+            state.contentsState.buffer().get(contentsStateBytes);
+        } else {
+            // For JellyBean and below a bug in MappedByteBufferAdapter causes rewind to not be
+            // propagated to the underlying ByteBuffer, and results in an underflow exception. See:
+            // http://b.android.com/53637.
+            for (int i = 0; i < state.contentsState.buffer().limit(); i++) {
+                contentsStateBytes[i] = state.contentsState.buffer().get(i);
+            }
+        }
 
         DataOutputStream dataOutputStream = null;
         FileOutputStream fileOutputStream = null;