AI 148333: Evidence from failures, and inspection of source, leads me to believe

that SharedPreferences has some non-thread-safe paths.  As a quick,
  brute-force workaround, I'm putting a global lock around our use of it.
  This is a bit inefficient, but cases of multiple threads writing to it
  should be very rare.
  Note, we don't have an explicit test for this (I will think about
  finding a way to write one), but the evidence of this failure is that
  after some amount of activity in the Email app, we see corruption in
  the string mSenderUri.
  BUG=1822859

Automated import of CL 148333

src/com/android/email/Account.java

@@ -112,6 +112,13 @@ public class Account implements Serializable {
     public void refresh(Preferences preferences) {
         mPreferences = preferences;
         
+        /**
+         * Note:  Until we have resolved the potential for synchronization failures in
+         * SharedPreferences, we're going to do a global lock around the read and write
+         * functions.
+         */
+        synchronized (Account.class) {
+
             mStoreUri = Utility.base64Decode(preferences.mSharedPreferences.getString(mUuid
                     + ".storeUri", null));
             mLocalStoreUri = preferences.mSharedPreferences.getString(mUuid + ".localStoreUri", null);
@@ -158,6 +165,7 @@ public class Account implements Serializable {
             mSyncWindow = preferences.mSharedPreferences.getInt(mUuid + KEY_SYNC_WINDOW, 
                     SYNC_WINDOW_USER);
         }
+    }
 
     public String getUuid() {
         return mUuid;
@@ -220,6 +228,12 @@ public class Account implements Serializable {
     }
 
     public void delete(Preferences preferences) {
+        /**
+         * Note:  Until we have resolved the potential for synchronization failures in
+         * SharedPreferences, we're going to do a global lock around the read and write
+         * functions.
+         */
+        synchronized (Account.class) {
             String[] uuids = preferences.mSharedPreferences.getString("accountUuids", "").split(",");
             StringBuffer sb = new StringBuffer();
             for (int i = 0, length = uuids.length; i < length; i++) {
@@ -258,10 +272,17 @@ public class Account implements Serializable {
 
             editor.commit();
         }
+    }
 
     public void save(Preferences preferences) {
         mPreferences = preferences;
         
+        /**
+         * Note:  Until we have resolved the potential for synchronization failures in
+         * SharedPreferences, we're going to do a global lock around the read and write
+         * functions.
+         */
+        synchronized (Account.class) {
             if (!preferences.mSharedPreferences.getString("accountUuids", "").contains(mUuid)) {
                 /*
                  * When the account is first created we assign it a unique account number. The
@@ -325,6 +346,7 @@ public class Account implements Serializable {
 
             editor.commit();
         }
+    }
 
     @Override
     public String toString() {