[downloads] Move platform specific code out of DownloadTargetDeterminer.

chrome/browser/download/download_confirmation_reason.h

+// Copyright 2016 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.
+
+#ifndef CHROME_BROWSER_DOWNLOAD_DOWNLOAD_CONFIRMATION_REASON_H_
+#define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_CONFIRMATION_REASON_H_
+
+enum class DownloadConfirmationReason {
+  NONE,
+  UNEXPECTED,       // Unexpected error.
+  SAVE_AS,          // "Save as" or "Save link as"
+  PREFERENCE,       // The user has set a preference requiring prompts for all
+                    // downloads.
+  NAME_TOO_LONG,    // The target name was too long and couldn't be truncated.
+  TARGET_CONFLICT,  // There were unresolved conflicts with the target path.
+  TARGET_NOT_WRITEABLE,  // The target path isn't writeable. Also may indicate
+                         // that a previous attempt to write to the path failed.
+  TARGET_NO_SPACE,  // The target path cannot accommodate a file of this size.
+};
+
+#endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_CONFIRMATION_REASON_H_