[DevTools] Create last agents on attach, modify InspectorDatabaseAgent to support it.

third_party/WebKit/Source/modules/webdatabase/DatabaseTracker.h

 /*
  * Copyright (C) 2007, 2008, 2013 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 24 matching lines @@
 #include "wtf/HashMap.h"
 #include "wtf/HashSet.h"
 #include "wtf/ThreadingPrimitives.h"
 #include "wtf/text/StringHash.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink {
 
 class Database;
 class DatabaseContext;
+class InspectorDatabaseAgent;
 class SecurityOrigin;
 
 class MODULES_EXPORT DatabaseTracker {
     WTF_MAKE_NONCOPYABLE(DatabaseTracker); USING_FAST_MALLOC(DatabaseTracker);
 public:
     static DatabaseTracker& tracker();
     // 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:
     // m_databaseGuard before quotaManager if both locks are needed.
     // m_openDatabaseMapGuard before quotaManager if both locks are needed.
     // m_databaseGuard and m_openDatabaseMapGuard currently don't overlap.
     // notificationMutex() is currently independent of the other locks.
 
     bool canEstablishDatabase(DatabaseContext*, const String& name, const String& displayName, unsigned long estimatedSize, DatabaseError&);
     String fullPathForDatabase(SecurityOrigin*, const String& name, bool createIfDoesNotExist = true);
 
     void addOpenDatabase(Database*);
     void removeOpenDatabase(Database*);
 
     unsigned long long getMaxSizeForDatabase(const Database*);
 
     void closeDatabasesImmediately(SecurityOrigin*, const String& name);
+    void registerAllDatabasesInInspector(InspectorDatabaseAgent*);

[michaeln, 2016/04/13 22:18:18]

It'd be nice to not have a dependency on the inspector here.

We could do this more generically with a function that returns a set of all open
Databases. I guess it'd need to be a GarbageCollectedFinalized set of some kind
which traced each database in the set as a Member<>?

Or maybe a forEachOpenDatabase(...) that takes a callback of some kind.

[dgozman, 2016/04/13 22:26:04]

I'd rather go for callback than Memeber<> collection to avoid all extra wrapping
and ownerhsip thoughts. I can't judge whether this particular class should not
depend on inspector, since there are a bunch of quite similarly named classes in
the same directory - it's hard to choose correct dependencies.

On the side note, I was surprised that DatabaseManager does not have a registry
of all databases and I had to look into DatabaseTracker.

 
     void prepareToOpenDatabase(Database*);
     void failedToOpenDatabase(Database*);
 
 private:
     using DatabaseSet = HashSet<UntracedMember<Database>>;
     using DatabaseNameMap = HashMap<String, DatabaseSet*>;
     using DatabaseOriginMap = HashMap<String, DatabaseNameMap*>;
     class CloseOneDatabaseImmediatelyTask;
 
     DatabaseTracker();
 
     void closeOneDatabaseImmediately(const String& originIdentifier, const String& name, Database*);
 
     Mutex m_openDatabaseMapGuard;
 
     // This map contains untraced pointers to a garbage-collected class. We can't
     // make this traceable because it is updated by multiple database threads.
     // See http://crbug.com/417990
     mutable OwnPtr<DatabaseOriginMap> m_openDatabaseMap;
 };
 
 } // namespace blink
 
 #endif // DatabaseTracker_h