Move creation of the various WebDatabaseTable types out of WebDatabase.

chrome/browser/webdata/web_database_table.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_WEBDATA_WEB_DATABASE_TABLE_H_
 #define CHROME_BROWSER_WEBDATA_WEB_DATABASE_TABLE_H_
 
 #include "base/logging.h"
 
 namespace sql {
 class Connection;
 class MetaTable;
 }
 
 // An abstract base class representing a table within a WebDatabase.
 // Each table should subclass this, adding type-specific methods as needed.
 class WebDatabaseTable {
  public:
-  WebDatabaseTable(sql::Connection* db, sql::MetaTable* meta_table);
+  // To look up a WebDatabaseTable of a certain type from WebDatabase,
+  // we use a void* key, so that we can simply use the address of one
+  // of the type's statics.
+  typedef void* TypeKey;
+
+  // The object is not ready for use until Init() has been called.
+  WebDatabaseTable();
   virtual ~WebDatabaseTable();
 
+  // Retrieves the TypeKey for the concrete subtype.
+  virtual TypeKey GetTypeKey() const = 0;
+
   // Attempts to initialize the table and returns true if successful.
-  virtual bool Init() = 0;
+  //
+  // The base class stores the members passed and always return true;
+  // subclasses may perform other initialization as needed.
+  virtual bool Init(sql::Connection* db, sql::MetaTable* meta_table);
 
   // In order to encourage developers to think about sync when adding or
   // or altering new tables, this method must be implemented. Please get in
   // contact with the sync team if you believe you're making a change that they
   // should be aware of (or if you could break something).
   // TODO(andybons): Implement something more robust.
   virtual bool IsSyncable() = 0;
 
   // Migrates this table to |version|. Returns false if there was
   // migration work to do and it failed, true otherwise.
   //
   // |app_locale| is the locale of the app. Passed as a parameter as
   // |it can only be safely queried on the UI thread.
   //
   // Implementations may set |*update_compatible_version| to true if
   // the compatible version should be changed to |version|.
   // Implementations should otherwise not modify this parameter.
   virtual bool MigrateToVersion(int version,
                                 const std::string& app_locale,
                                 bool* update_compatible_version) = 0;
 
  protected:
+  // Non-owning. These are owned by WebDatabase, valid as long as that
+  // class exists. Since lifetime of WebDatabaseTable objects slightly
+  // exceeds that of WebDatabase, they should not be used in
+  // ~WebDatabaseTable.
   sql::Connection* db_;
   sql::MetaTable* meta_table_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(WebDatabaseTable);
 };
 
 #endif  // CHROME_BROWSER_WEBDATA_WEB_DATABASE_TABLE_H_