Make VEA test support videos with different coded size and visible size

base/files/memory_mapped_file_posix.cc

 // Copyright 2013 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.
 
 #include "base/files/memory_mapped_file.h"
 
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include <unistd.h>
 
@@ skipping 44 matching lines @@
       return false;
     }
 
     map_start = static_cast<off_t>(aligned_start);
     map_size = static_cast<size_t>(aligned_size);
     length_ = static_cast<size_t>(region.size);
   }
 
   data_ = static_cast<uint8*>(mmap(NULL,
                                    map_size,
-                                   PROT_READ,
+                                   PROT_READ | PROT_WRITE,
                                    MAP_SHARED,
                                    file_.GetPlatformFile(),
                                    map_start));
   if (data_ == MAP_FAILED) {
     DPLOG(ERROR) << "mmap " << file_.GetPlatformFile();
     return false;
   }
 
   data_ += data_offset;
   return true;
 }
 
 void MemoryMappedFile::CloseHandles() {
   ThreadRestrictions::AssertIOAllowed();
 
   if (data_ != NULL)
     munmap(data_, length_);
   file_.Close();
 
   data_ = NULL;
   length_ = 0;
 }
 
 }  // namespace base