chrome/browser/media_galleries/fileapi: Change ScopedTempDir::path() to GetPath()

path() is being deprecated, GetPath() has better checking against wrong use.

For more context, see https://codereview.chromium.org/2275553005/.

BUG=640599
TBR=kinuko@chromium.org

Review-Url: https://codereview.chromium.org/2385693002
Cr-Commit-Position: refs/heads/master@{#422117}
1 file changed