make base::SharedMemoryHandle a class on POSIX.

base/memory/shared_memory_android.cc

Index: base/memory/shared_memory_android.cc
diff --git a/base/memory/shared_memory_android.cc b/base/memory/shared_memory_android.cc
index 6f1d9cb874c664891a1cfaa71920b803ef4c8eaa..49289f704b392d2e15ef594bdd11e83f140ead9f 100644
--- a/base/memory/shared_memory_android.cc
+++ b/base/memory/shared_memory_android.cc
@@ -18,21 +18,22 @@ namespace base {
 // are closed, the memory buffer will go away.
 
 bool SharedMemory::Create(const SharedMemoryCreateOptions& options) {
-  DCHECK_EQ(-1, mapped_file_ );
+  DCHECK(!shm_.IsValid());
 
   if (options.size > static_cast<size_t>(std::numeric_limits<int>::max()))
     return false;
 
   // "name" is just a label in ashmem. It is visible in /proc/pid/maps.
-  mapped_file_ = ashmem_create_region(
+  int fd = ashmem_create_region(
       options.name_deprecated == NULL ? "" : options.name_deprecated->c_str(),
       options.size);
-  if (-1 == mapped_file_) {
+  shm_ = SharedMemoryHandle::ImportHandle(fd);
+  if (!shm_.IsValid()) {
     DLOG(ERROR) << "Shared memory creation failed";
     return false;
   }
 
-  int err = ashmem_set_prot_region(mapped_file_,
+  int err = ashmem_set_prot_region(shm_.GetHandle(),
                                    PROT_READ | PROT_WRITE | PROT_EXEC);
   if (err < 0) {
     DLOG(ERROR) << "Error " << err << " when setting protection of ashmem";
@@ -41,7 +42,7 @@ bool SharedMemory::Create(const SharedMemoryCreateOptions& options) {
 
   // Android doesn't appear to have a way to drop write access on an ashmem
   // segment for a single descriptor.  http://crbug.com/320865
-  readonly_mapped_file_ = dup(mapped_file_);
+  readonly_mapped_file_ = dup(shm_.GetHandle());
   if (-1 == readonly_mapped_file_) {
     DPLOG(ERROR) << "dup() failed";
     return false;