Fix history importing by delaying DownloadManager creation.

content/browser/download/download_id.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_DOWNLOAD_DOWNLOAD_ID_H_
 #define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_ID_H_
 #pragma once
 
 #include <iosfwd>
 
 #include "base/hash_tables.h"
 #include "content/common/content_export.h"
 
-class DownloadManager;
-
 // DownloadId combines per-profile Download ids with an indication of which
 // profile in order to be globally unique. DownloadIds are not persistent across
 // sessions, but their local() field is.
 class DownloadId {
  public:
   static DownloadId Invalid() { return DownloadId(NULL, -1); }
 
-  DownloadId(const DownloadManager* manager, int32 local_id)
-    : manager_(manager),
+  // Domain separates spaces of local ids.
+  typedef const void* Domain;
+
+  DownloadId(Domain domain, int32 local_id)
+    : domain_(domain),
       local_id_(local_id) {
   }
 
   // Return the per-profile and persistent part of this DownloadId.
   int32 local() const { return local_id_; }
 
   // Returns true if this DownloadId has been allocated and could possibly refer
   // to a DownloadItem that exists.
-  bool IsValid() const { return ((manager_ != NULL) && (local_id_ >= 0)); }
+  bool IsValid() const { return ((domain_ != NULL) && (local_id_ >= 0)); }
 
   // The following methods (operator==, hash(), copy, and assign) provide
   // support for STL containers such as hash_map.
 
   bool operator==(const DownloadId& that) const {
     return ((that.local_id_ == local_id_) &&
-            (that.manager_ == manager_));
+            (that.domain_ == domain_));
   }
   bool operator<(const DownloadId& that) const {
-    // Even though DownloadManager* < DownloadManager* is not well defined and
+    // Even though Domain::operator< is not well defined and
     // GCC does not require it for hash_map, MSVC requires operator< for
     // hash_map. We don't ifdef it out here because we will probably make a
     // set<DownloadId> at some point, when GCC will require it.
-    return ((manager_ < that.manager_) ||
-            ((manager_ == that.manager_) && (local_id_ < that.local_id_)));
+    return ((domain_ < that.domain_) ||
+            ((domain_ == that.domain_) && (local_id_ < that.local_id_)));
   }
 
   size_t hash() const {
     // The top half of manager is unlikely to be distinct, and the user is
     // unlikely to have >64K downloads. If these assumptions are incorrect, then
     // DownloadFileManager's hash_map might have a few collisions, but it will
     // use operator== to safely disambiguate.
-    return reinterpret_cast<size_t>(manager_) +
+    return reinterpret_cast<size_t>(domain_) +
            (static_cast<size_t>(local_id_) << (4 * sizeof(size_t)));
   }
 
  private:
   // DownloadId is used mostly off the UI thread, so manager's methods can't be
   // called, but the pointer can be compared.
-  const DownloadManager* manager_;
+  Domain domain_;
 
   int32 local_id_;
 
   friend CONTENT_EXPORT std::ostream& operator<<(std::ostream& out,
                                                  const DownloadId& global_id);
 
   // Allow copy and assign.
 };
 
 // Allow logging DownloadIds. Looks like "0x01234567:42".
 CONTENT_EXPORT std::ostream& operator<<(std::ostream& out,
                                         const DownloadId& global_id);
 
 // Allow using DownloadIds as keys in hash_maps.
 namespace BASE_HASH_NAMESPACE {
 #if defined(COMPILER_GCC)
 template<> struct hash<DownloadId> {
   std::size_t operator()(const DownloadId& id) const {
     return id.hash();
   }
 };
 #elif defined(COMPILER_MSVC)
 inline size_t hash_value(const DownloadId& id) {
   return id.hash();
 }
 #endif  // COMPILER
 }
 #endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_ID_H_