Rename isolated_output to test_output and add a method to get the test_output directory.

webrtc/test/testsupport/isolated_output.h

Index: webrtc/test/testsupport/isolated_output.h
diff --git a/webrtc/test/testsupport/isolated_output.h b/webrtc/test/testsupport/isolated_output.h
deleted file mode 100644
index f4e9695157101ae940d41387b9ee137028996675..0000000000000000000000000000000000000000
--- a/webrtc/test/testsupport/isolated_output.h
+++ /dev/null
@@ -1,35 +0,0 @@
-/*
- *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree. An additional intellectual property rights grant can be found
- *  in the file PATENTS.  All contributing project authors may
- *  be found in the AUTHORS file in the root of the source tree.
- */
-
-#ifndef WEBRTC_TEST_TESTSUPPORT_ISOLATED_OUTPUT_H_
-#define WEBRTC_TEST_TESTSUPPORT_ISOLATED_OUTPUT_H_
-
-#include <stdlib.h>
-
-#include <string>
-
-namespace webrtc {
-namespace test {
-
-// Writes a |length| bytes array |buffer| to |filename| in isolated output
-// directory defined by swarming. If the file is existing, content will be
-// appended. Otherwise a new file will be created. This function returns false
-// if isolated output directory has not been defined, or |filename| indicates an
-// invalid or non-writable file, or underlying file system errors.
-bool WriteIsolatedOutput(const char* filename,
-                         const uint8_t* buffer,
-                         size_t length);
-
-bool WriteIsolatedOutput(const char* filename, const std::string& content);
-
-}  // namespace test
-}  // namespace webrtc
-
-#endif  // WEBRTC_TEST_TESTSUPPORT_ISOLATED_OUTPUT_H_