diff --git a/storage/public/Makefile.in b/storage/public/Makefile.in
index b669d956721e..6dfcfc69aeeb 100644
--- a/storage/public/Makefile.in
+++ b/storage/public/Makefile.in
@@ -57,4 +57,8 @@ XPIDLSRCS = \
 	mozIStorageValueArray.idl \
 	$(NULL)
 
+EXPORTS = \
+	mozStorageHelper.h \
+	$(NULL)
+
 include $(topsrcdir)/config/rules.mk
diff --git a/storage/public/mozIStorageConnection.idl b/storage/public/mozIStorageConnection.idl
index 2957e95be2d3..15c55fa83f6f 100644
--- a/storage/public/mozIStorageConnection.idl
+++ b/storage/public/mozIStorageConnection.idl
@@ -54,7 +54,7 @@ interface mozIStorageConnection : nsISupports {
   readonly attribute boolean connectionReady;
 
   /**
-   * the current database filename
+   * the current database filename. Empty if the database is in-memory
    */
   readonly attribute AUTF8String databaseName;
 
@@ -113,11 +113,19 @@ interface mozIStorageConnection : nsISupports {
   readonly attribute boolean transactionInProgress;
 
   /**
-   * Begin a new transaction.  If a transaction is active,
-   * @throws NS_ERROR_STORAGE_INVALID_OPERATION.
+   * Begin a new transaction.  sqlite default transactions are deferred.
+   * If a transaction is active, throws an error.
    */
   void beginTransaction ();
 
+  /**
+   * Begins a new transaction with the given type.
+   */
+  const PRInt32 TRANSACTION_DEFERRED = 0;
+  const PRInt32 TRANSACTION_IMMEDIATE = 1;
+  const PRInt32 TRANSACTION_EXCLUSIVE = 2;
+  void beginTransactionAs (in PRInt32 transactionType);
+
   /**
    * Commits the current transaction.  If no transaction is active,
    * @throws NS_ERROR_STORAGE_NO_TRANSACTION.
diff --git a/storage/src/mozStorageConnection.cpp b/storage/src/mozStorageConnection.cpp
index 9a11ab5505ae..2a1518f0d2d5 100644
--- a/storage/src/mozStorageConnection.cpp
+++ b/storage/src/mozStorageConnection.cpp
@@ -80,24 +80,31 @@ void tracefunc (void *closure, const char *stmt)
 }
 #endif
 
+/**
+ * Actually creates the connection from the DB. Called by mozStorageService.
+ * You can pass a NULL database file in to get an sqlite in-memory database.
+ */
 NS_IMETHODIMP
 mozStorageConnection::Initialize(nsIFile *aDatabaseFile)
 {
-    NS_ENSURE_ARG_POINTER(aDatabaseFile);
-
     NS_ASSERTION (!mDBConn, "Initialize called on already opened database!");
 
     int srv;
     nsresult rv;
 
-    rv = aDatabaseFile->GetNativeLeafName(mDatabaseName);
-    NS_ENSURE_SUCCESS(rv, rv);
+    if (aDatabaseFile) {
+        rv = aDatabaseFile->GetNativeLeafName(mDatabaseName);
+        NS_ENSURE_SUCCESS(rv, rv);
 
-    nsCAutoString nativePath;
-    rv = aDatabaseFile->GetNativePath(nativePath);
-    NS_ENSURE_SUCCESS(rv, rv);
+        nsCAutoString nativePath;
+        rv = aDatabaseFile->GetNativePath(nativePath);
+        NS_ENSURE_SUCCESS(rv, rv);
 
-    srv = sqlite3_open (nativePath.get(), &mDBConn);
+        srv = sqlite3_open (nativePath.get(), &mDBConn);
+    } else {
+        // in memory database requested, sqlite uses a magic file name
+        srv = sqlite3_open (":memory:", &mDBConn);
+    }
     if (srv != SQLITE_OK) {
         mDBConn = nsnull;
         return NS_ERROR_FAILURE; // XXX error code
@@ -252,7 +259,7 @@ mozStorageConnection::TableExists(const nsACString& aSQLStatement, PRBool *_retv
  **/
 
 NS_IMETHODIMP
-mozStorageConnection::GetTransactionInProgress(PRInt32 *_retval)
+mozStorageConnection::GetTransactionInProgress(PRBool *_retval)
 {
     *_retval = mTransactionInProgress;
     return NS_OK;
@@ -270,6 +277,30 @@ mozStorageConnection::BeginTransaction()
     return rv;
 }
 
+NS_IMETHODIMP
+mozStorageConnection::BeginTransactionAs(PRInt32 aTransactionType)
+{
+    if (mTransactionInProgress)
+        return NS_ERROR_FAILURE; // XXX error code
+    nsresult rv;
+    switch(aTransactionType) {
+        case TRANSACTION_DEFERRED:
+            rv = ExecuteSimpleSQL(NS_LITERAL_CSTRING("BEGIN DEFERRED"));
+            break;
+        case TRANSACTION_IMMEDIATE:
+            rv = ExecuteSimpleSQL(NS_LITERAL_CSTRING("BEGIN IMMEDIATE"));
+            break;
+        case TRANSACTION_EXCLUSIVE:
+            rv = ExecuteSimpleSQL(NS_LITERAL_CSTRING("BEGIN EXCLUSIVE"));
+            break;
+        default:
+            return NS_ERROR_ILLEGAL_VALUE;
+    }
+    if (NS_SUCCEEDED(rv))
+        mTransactionInProgress = PR_TRUE;
+    return NS_OK;
+}
+
 NS_IMETHODIMP
 mozStorageConnection::CommitTransaction()
 {
diff --git a/storage/src/mozStorageService.cpp b/storage/src/mozStorageService.cpp
index 24e6ef2100e6..77cb5912ed52 100644
--- a/storage/src/mozStorageService.cpp
+++ b/storage/src/mozStorageService.cpp
@@ -38,6 +38,7 @@
 
 #include "mozStorageService.h"
 #include "mozStorageConnection.h"
+#include "plstr.h"
 
 #include "sqlite3.h"
 
@@ -67,10 +68,23 @@ mozStorageService::GetProfileStorage(const char *aStorageKey, mozIStorageConnect
     nsresult rv;
 
     nsCOMPtr<nsIFile> storageFile;
-    rv = NS_GetSpecialDirectory(NS_APP_STORAGE_50_FILE, getter_AddRefs(storageFile));
-    if (NS_FAILED(rv)) {
-        // teh wtf?
-        return rv;
+    if (PL_strcmp(aStorageKey, "memory") == 0) {
+        // just fall through with NULL storageFile, this will cause the storage
+        // connection to use a memory DB.
+    } else if (PL_strcmp(aStorageKey, "profile") == 0) {
+
+        rv = NS_GetSpecialDirectory(NS_APP_STORAGE_50_FILE, getter_AddRefs(storageFile));
+        if (NS_FAILED(rv)) {
+            // teh wtf?
+            return rv;
+        }
+
+        nsString filename;
+        storageFile->GetPath(filename);
+        nsCString filename8 = NS_ConvertUTF16toUTF8(filename.get());
+        // fall through to DB initialization
+    } else {
+        return NS_ERROR_INVALID_ARG;
     }
 
     mozStorageConnection *msc = new mozStorageConnection();