Implement WriteAtomically using write/fsync on all platforms, and enable

file unittests on Fuchsia

Author: George Wright

fml/platform/posix/file_posix.cc

@@ -206,15 +206,12 @@ bool WriteAtomically(const fml::UniqueFD& base_directory,
     return false;
   }
 
-  FileMapping mapping(temp_file, {FileMapping::Protection::kWrite});
-  if (mapping.GetMutableMapping() == nullptr ||
-      data.GetSize() != mapping.GetSize()) {
+  ssize_t size = ::write(temp_file.get(), data.GetMapping(), data.GetSize());
+  if (size == -1) {
     return false;
   }
 
-  ::memcpy(mapping.GetMutableMapping(), data.GetMapping(), data.GetSize());
-
-  if (::msync(mapping.GetMutableMapping(), data.GetSize(), MS_SYNC) != 0) {
+  if (::fsync(temp_file.get()) != 0) {
     return false;
   }
 

testing/fuchsia/run_tests.sh

@@ -91,7 +91,7 @@ echo "$(date) START:fml_tests ---------------------------------------"
 ./fuchsia_ctl -d $device_name test \
     -f fml_tests-0.far  \
     -t fml_tests \
-    -a "--gtest_filter=-MessageLoop*:Message*:FileTest*" \
+    -a "--gtest_filter=-MessageLoop*:Message*" \
     --identity-file $pkey \
     --timeout-seconds 300 \
     --packages-directory packages