Crash fix in fileapi::FileSystemOperation::DidGetUsageAndQuotaAndRunTask

https://chromiumcodereview.appspot.com/10008047 introduced delete-with-inflight-tasks in Write sequence but I failed to convert this callback to use WeakPtr().

BUG=128178
TEST=manual test

Review URL: https://chromiumcodereview.appspot.com/10408006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@137635 0039d316-1c4b-4281-b951-d872f2087c98
FileSystemOperation::TaskParamsForDidGetQuota::TaskParamsForDidGetQuota()
    : type(kFileSystemTypeUnknown) {
}

FileSystemOperation::TaskParamsForDidGetQuota::TaskParamsForDidGetQuota()
    : type(kFileSystemTypeUnknown) {
}
