Avoid disk reads in TabPersistentStore for max tab_id.

chrome/android/java/src/org/chromium/chrome/browser/tab/TabIdManager.java

Index: chrome/android/java/src/org/chromium/chrome/browser/tab/TabIdManager.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/tab/TabIdManager.java b/chrome/android/java/src/org/chromium/chrome/browser/tab/TabIdManager.java
index 30113b1e2c6141a9e83b5a1873847271dfa0be89..4ccdf7cef0c3062dfc1bfef78c219a9814457463 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/tab/TabIdManager.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/tab/TabIdManager.java
@@ -10,6 +10,7 @@ import android.preference.PreferenceManager;
 
 import org.chromium.base.ApplicationStatus;
 import org.chromium.base.VisibleForTesting;
+import org.chromium.chrome.browser.tabmodel.TabModel;
 
 import java.util.concurrent.atomic.AtomicInteger;
 
@@ -38,6 +39,8 @@ public class TabIdManager {
     private final Context mContext;
     private final AtomicInteger mIdCounter = new AtomicInteger();
 
+    private SharedPreferences mPreferences;
+
     /** Returns the Singleton instance of the TabIdManager. */
     public static TabIdManager getInstance() {
         return getInstance(ApplicationStatus.getApplicationContext());
@@ -80,14 +83,7 @@ public class TabIdManager {
         // It's possible idCounter has been incremented between the get and the add but that's OK --
         // in the worst case mIdCounter will just be overly incremented.
         mIdCounter.addAndGet(diff);
-        updateSharedPreference();
-    }
-
-    private void updateSharedPreference() {
-        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(mContext);
-        SharedPreferences.Editor editor = prefs.edit();
-        editor.putInt(PREF_NEXT_ID, mIdCounter.get());
-        editor.apply();
+        mPreferences.edit().putInt(PREF_NEXT_ID, mIdCounter.get()).apply();
     }
 
     private TabIdManager(Context context) {
@@ -96,7 +92,7 @@ public class TabIdManager {
         // Read the shared preference.  This has to be done on the critical path to ensure that the
         // myriad Activities that serve as entries into Chrome are all synchronized on the correct
         // maximum Tab ID.
-        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(mContext);
-        mIdCounter.set(prefs.getInt(PREF_NEXT_ID, 0));
+        mPreferences = PreferenceManager.getDefaultSharedPreferences(mContext);
+        mIdCounter.set(mPreferences.getInt(PREF_NEXT_ID, 0));
     }
 }