Update from https://crrev.com/308331

base/memory/shared_memory.h

 // Copyright (c) 2012 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_MEMORY_SHARED_MEMORY_H_
 #define BASE_MEMORY_SHARED_MEMORY_H_
 
 #include "build/build_config.h"
 
 #include <string>
@@ skipping 182 matching lines @@
   SharedMemoryHandle handle() const;
 
 #if defined(OS_POSIX) && !defined(OS_NACL)
   // Returns a unique identifier for this shared memory segment. Inode numbers
   // are technically only unique to a single filesystem. However, we always
   // allocate shared memory backing files from the same directory, so will end
   // up on the same filesystem.
   SharedMemoryId id() const { return inode_; }
 #endif
 
-  // Closes the open shared memory segment.
+  // Closes the open shared memory segment. The memory will remain mapped if
+  // it was previously mapped.
   // It is safe to call Close repeatedly.
   void Close();
 
   // Shares the shared memory to another process.  Attempts to create a
   // platform-specific new_handle which can be used in a remote process to read
   // the shared memory file.  new_handle is an output parameter to receive the
   // handle for use in the remote process.
   //
   // |*this| must have been initialized using one of the Create*() or Open()
   // methods with share_read_only=true. If it was constructed from a
@@ skipping 102 matching lines @@
   }
 
  private:
   SharedMemory* shared_memory_;
   DISALLOW_COPY_AND_ASSIGN(SharedMemoryAutoLockDeprecated);
 };
 
 }  // namespace base
 
 #endif  // BASE_MEMORY_SHARED_MEMORY_H_