Update from https://crrev.com/308331

base/memory/shared_memory_posix.cc

Index: base/memory/shared_memory_posix.cc
diff --git a/base/memory/shared_memory_posix.cc b/base/memory/shared_memory_posix.cc
index 0358e63e33843be8973fd0f3d01097e038bbb818..fd26ad19ffbe1e3268d9b4165dd3591b4b0f6042 100644
--- a/base/memory/shared_memory_posix.cc
+++ b/base/memory/shared_memory_posix.cc
@@ -80,6 +80,7 @@ SharedMemory::SharedMemory(SharedMemoryHandle handle, bool read_only,
 }
 
 SharedMemory::~SharedMemory() {
+  Unmap();
   Close();
 }
 
@@ -331,8 +332,6 @@ SharedMemoryHandle SharedMemory::handle() const {
 }
 
 void SharedMemory::Close() {
-  Unmap();
-
   if (mapped_file_ > 0) {
     if (close(mapped_file_) < 0)
       PLOG(ERROR) << "close";
@@ -468,8 +467,10 @@ bool SharedMemory::ShareToProcessCommon(ProcessHandle process,
   new_handle->fd = new_fd;
   new_handle->auto_close = true;
 
-  if (close_self)
+  if (close_self) {
+    Unmap();
     Close();
+  }
 
   return true;
 }