Cache state directory in TabPersistentStore.

chrome/android/java/src/org/chromium/chrome/browser/tabmodel/TabPersistentStore.java

Index: chrome/android/java/src/org/chromium/chrome/browser/tabmodel/TabPersistentStore.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/tabmodel/TabPersistentStore.java b/chrome/android/java/src/org/chromium/chrome/browser/tabmodel/TabPersistentStore.java
index 0e821b961949847f1136c565c972d7803e49613b..011c1e212c420ed6887a3244e06d6525f964a3e4 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/tabmodel/TabPersistentStore.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/tabmodel/TabPersistentStore.java
@@ -106,6 +106,8 @@ public class TabPersistentStore extends TabPersister {
     private boolean mCancelNormalTabLoads = false;
     private boolean mCancelIncognitoTabLoads = false;
 
+    private File mStateDirectory;
+
     // Keys are the original tab indexes, values are the tab ids.
     private SparseIntArray mNormalTabsRestored;
     private SparseIntArray mIncognitoTabsRestored;
@@ -143,7 +145,10 @@ public class TabPersistentStore extends TabPersister {
 
     @Override
     public File getStateDirectory() {
-        return getStateDirectory(mContext, mSelectorIndex);
+        if (mStateDirectory == null) {
+            mStateDirectory = getStateDirectory(mContext, mSelectorIndex);
+        }
+        return mStateDirectory;
     }
 
     /**