Fixed the bug that Drive doesn't appear on Files App on epehmeral mode.

components/drive/chromeos/file_cache.cc

 // 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.
 
 #include "components/drive/chromeos/file_cache.h"
 
 #include <linux/fs.h>
 #include <sys/ioctl.h>
 #include <sys/xattr.h>
 
@@ skipping 34 matching lines @@
 std::string GetIdFromPath(const base::FilePath& path) {
   return util::UnescapeCacheFileName(path.BaseName().AsUTF8Unsafe());
 }
 
 base::FilePath GetPathForId(const base::FilePath& cache_directory,
                             const std::string& id) {
   return cache_directory.Append(
       base::FilePath::FromUTF8Unsafe(util::EscapeCacheFileName(id)));
 }
 
+// Returns if the filesystem backing |path| supports file attributes.
+// This will return false if the filesystem is for example tmpfs, which is used
+// for ephemeral mode.
+bool IsFileAttributesSupported(const base::FilePath& path) {
+  getxattr(path.value().c_str(), "user.foo", nullptr, 0);

[hashimoto, 2016/10/14 04:16:49]

Please check that getxattr actually fails.

[oka, 2016/10/14 04:36:06]

Done.

+  return errno != ENOTSUP;
+}
+
 // Sets extended file attribute as |name| |value| pair.
 bool SetExtendedFileAttributes(const base::FilePath& path,
     const std::string& name, const std::string& value) {
+  if (!IsFileAttributesSupported(path)) {

[hashimoto, 2016/10/14 04:16:49]

Isn't it better to check this at the beginning of MarkAsDriveCacheDir instead?

[oka, 2016/10/14 04:36:05]

Done.

+    return true;
+  }
   return setxattr(path.value().c_str(), name.c_str(), value.c_str(),
       value.size() + 1, 0) == 0;
 }
 
 // Changes attributes of the file with |flags|, e.g. FS_NODUMP_FL (cryptohome
 // will remove Drive caches with this attribute).
 // See linux/fs.h for available flags, and chattr(1) which does similar thing.
 // Returns whether operation succeeded.
 bool SetFileAttributes(const base::FilePath& path, FileAttributes flags) {
   base::File file(path, base::File::FLAG_OPEN | base::File::FLAG_READ);
@@ skipping 19 matching lines @@
   FileAttributes flags = 0;
   if (ioctl(file.GetPlatformFile(), FS_IOC_GETFLAGS, &flags) < 0) {
     PLOG(ERROR) << "ioctl: " << path.value();
     return -1;
   }
   return flags;
 }
 
 // Marks the cache file to be removable by cryptohome.
 bool SetRemovable(const base::FilePath& path) {
+  if (!IsFileAttributesSupported(path)) {

[hashimoto, 2016/10/14 04:16:48]

It'd be nice to have a brief comment to justify this early-return.

[oka, 2016/10/14 04:36:05]

Done.

+    return true;
+  }
   FileAttributes flags = GetFileAttributes(path);
   if (flags < 0) return false;
   if ((flags & FS_NODUMP_FL) == FS_NODUMP_FL) return true;
 
   return SetFileAttributes(path, flags | FS_NODUMP_FL);
 }
 
 // Marks the cache file to be unremovable by cryptohome.
 bool UnsetRemovable(const base::FilePath& path) {
+  if (!IsFileAttributesSupported(path)) {

[hashimoto, 2016/10/14 04:16:48]

ditto.

[oka, 2016/10/14 04:36:06]

Done.

+    return true;
+  }
   FileAttributes flags = GetFileAttributes(path);
   if (flags < 0) return false;
   if ((flags & FS_NODUMP_FL) == 0) return true;
 
   return SetFileAttributes(path, flags & ~FS_NODUMP_FL);
 }
 
 // Marks |path| as drive cache dir.
 // Returns if the operation succeeded.
 bool MarkAsDriveCacheDir(const base::FilePath& path) {
@@ skipping 789 matching lines @@
 
 bool FileCache::IsEvictable(const std::string& id, const ResourceEntry& entry) {
   return IsPresent(entry) &&
          !entry.file_specific_info().cache_state().is_pinned() &&
          !entry.file_specific_info().cache_state().is_dirty() &&
          !mounted_files_.count(id);
 }
 
 }  // namespace internal
 }  // namespace drive