Port visitedlink tests to Linux. Also make them pass on Linux, which

base/shared_memory.h

 // Copyright (c) 2006-2008 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 BASE_SHARED_MEMORY_H_
 #define BASE_SHARED_MEMORY_H_
 
 #include "build/build_config.h"
 
 #if defined(OS_POSIX)
@@ skipping 40 matching lines @@
   SharedMemory(SharedMemoryHandle handle, bool read_only,
       base::ProcessHandle process);
 
   // Destructor.  Will close any open files.
   ~SharedMemory();
 
   // Return true iff the given handle is valid (i.e. not the distingished
   // invalid value; NULL for a HANDLE and -1 for a file descriptor)
   static bool IsHandleValid(const SharedMemoryHandle& handle);
 
+  // Return invalid handle (see comment above for exact definition).
+  static SharedMemoryHandle NULLHandle();
+
   // Creates or opens a shared memory segment based on a name.
   // If read_only is true, opens the memory as read-only.
   // If open_existing is true, and the shared memory already exists,
   // opens the existing shared memory and ignores the size parameter.
   // If name is the empty string, use a unique name.
   // Returns true on success, false on failure.
   bool Create(const std::wstring& name, bool read_only, bool open_existing,
               size_t size);
 
   // Deletes resources associated with a shared memory segment based on name.
@@ skipping 123 matching lines @@
   }
 
  private:
   SharedMemory* shared_memory_;
   DISALLOW_EVIL_CONSTRUCTORS(SharedMemoryAutoLock);
 };
 
 }  // namespace base
 
 #endif  // BASE_SHARED_MEMORY_H_