Remove obviously unneeded forward declarations from headers under src/{app,base,net}.

net/disk_cache/block_files.h

 // Copyright (c) 2010 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.
 
 // See net/disk_cache/disk_cache.h for the public interface.
 
 #ifndef NET_DISK_CACHE_BLOCK_FILES_H__
 #define NET_DISK_CACHE_BLOCK_FILES_H__
 #pragma once
 
 #include <vector>
 
 #include "base/file_path.h"
 #include "base/gtest_prod_util.h"
 #include "net/disk_cache/addr.h"
 #include "net/disk_cache/mapped_file.h"
 
 namespace disk_cache {
 
-class EntryImpl;
-
 // This class handles the set of block-files open by the disk cache.
 class BlockFiles {
  public:
   explicit BlockFiles(const FilePath& path)
       : init_(false), zero_buffer_(NULL), path_(path) {}
   ~BlockFiles();
 
   // Performs the object initialization. create_files indicates if the backing
   // files should be created or just open.
   bool Init(bool create_files);
@@ skipping 55 matching lines @@
   FRIEND_TEST_ALL_PREFIXES(DiskCacheTest, BlockFiles_ZeroSizeFile);
   FRIEND_TEST_ALL_PREFIXES(DiskCacheTest, BlockFiles_InvalidFile);
   FRIEND_TEST_ALL_PREFIXES(DiskCacheTest, BlockFiles_Stats);
 
   DISALLOW_COPY_AND_ASSIGN(BlockFiles);
 };
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_BLOCK_FILES_H__