Make the DatabaseTracker thread-safe.

WebCore/storage/DatabaseTracker.h

Index: WebCore/storage/DatabaseTracker.h
===================================================================
--- WebCore/storage/DatabaseTracker.h	(revision 55036)
+++ WebCore/storage/DatabaseTracker.h	(working copy)
@@ -60,9 +60,11 @@
 class DatabaseTracker : public Noncopyable {
 public:
     static DatabaseTracker& tracker();
-    // FIXME: Due to workers having multiple threads in a single process sharing
-    // a DatabaseTracker, this singleton will have to be synchronized or moved
-    // to TLS.
+    // This singleton will potentially be used from multiple worker threads and the page's context thread simultaneously.  To keep this safe, it's
+    // currently using 4 locks.  In order to avoid deadlock when taking multiple locks, you must take them in the correct order:
+    // originQuotaManager() before m_databaseGuard or m_openDatabaseMapGuard
+    // m_databaseGuard before m_openDatabaseMapGuard
+    // notificationMutex() is currently independent of the other locks.
 
     bool canEstablishDatabase(ScriptExecutionContext*, const String& name, const String& displayName, unsigned long estimatedSize);
     void setDatabaseDetails(SecurityOrigin*, const String& name, const String& displayName, unsigned long estimatedSize);
@@ -87,7 +89,7 @@
 #if !PLATFORM(CHROMIUM)
 public:
     void setDatabaseDirectoryPath(const String&);
-    const String& databaseDirectoryPath() const;
+    String databaseDirectoryPath() const;
 
     void origins(Vector<RefPtr<SecurityOrigin> >& result);
     bool databaseNamesForOrigin(SecurityOrigin*, Vector<String>& result);
@@ -114,6 +116,13 @@
     bool hasEntryForOrigin(SecurityOrigin*);
 
 private:
+    OriginQuotaManager& originQuotaManagerNoLock();
+    bool hasEntryForOriginNoLock(SecurityOrigin* origin);
+    String fullPathForDatabaseNoLock(SecurityOrigin*, const String& name, bool createIfDoesNotExist);
+    bool databaseNamesForOriginNoLock(SecurityOrigin* origin, Vector<String>& resultVector);
+    unsigned long long usageForOriginNoLock(SecurityOrigin* origin);
+    unsigned long long quotaForOriginNoLock(SecurityOrigin* origin);
+
     String trackerDatabasePath() const;
     void openTrackerDatabase(bool createIfDoesNotExist);
 
@@ -126,10 +135,11 @@
 
     bool deleteDatabaseFile(SecurityOrigin*, const String& name);
 
+    // This lock protects m_database, m_quotaMap, and m_proposedDatabases.
+    Mutex m_databaseGuard;
     SQLiteDatabase m_database;
 
     typedef HashMap<RefPtr<SecurityOrigin>, unsigned long long, SecurityOriginHash> QuotaMap;
-    Mutex m_quotaMapGuard;
     mutable OwnPtr<QuotaMap> m_quotaMap;
 
     OwnPtr<OriginQuotaManager> m_quotaManager;
@@ -138,12 +148,9 @@
 
     DatabaseTrackerClient* m_client;
 
-    std::pair<SecurityOrigin*, DatabaseDetails>* m_proposedDatabase;
+    typedef std::pair<SecurityOrigin*, DatabaseDetails> ProposedDatabase;
+    HashSet<ProposedDatabase*> m_proposedDatabases;
 
-#ifndef NDEBUG
-    ThreadIdentifier m_thread;
-#endif
-
     static void scheduleForNotification();
     static void notifyDatabasesChanged(void*);
 #endif // !PLATFORM(CHROMIUM)