[libfuzzer] Update documentation on UBSan options and Upload Corpus section.

testing/libfuzzer/clusterfuzz.md

Index: testing/libfuzzer/clusterfuzz.md
diff --git a/testing/libfuzzer/clusterfuzz.md b/testing/libfuzzer/clusterfuzz.md
index 513b45eaf2d2f6b169695af6f9f9cdb7bca34234..527907dcc98c75daf0303ab9a2f8a5f874f8ef5d 100644
--- a/testing/libfuzzer/clusterfuzz.md
+++ b/testing/libfuzzer/clusterfuzz.md
@@ -35,6 +35,33 @@ metrics as well as provides links to crashes and coverage reports. The informati
 is collected every 30 minutes.
 
 
+## Upload Corpus
+There are two types of corpus used by libFuzzers at ClusterFuzz:

[Martin Barbella, 2016/04/19 15:44:41]

ClusterFuzz uses two corpus types with libFuzzer:

[mmoroz, 2016/04/19 17:46:36]

Done.

+
+1) **Seed** (or **static**) corpus: files manually uploaded by developers.
+ClusterFuzz uses these files for fuzzing but doesn't delete/overwrite them.
+
+2) **General** (or **working**) corpus: files generated by fuzzers themselves.
+These corpus files are frequently modified during fuzzing sessions and can be
+deleted during corpus minimization.
+
+Literally, a fuzzer has two input corpus directories (seed and general), but

[Martin Barbella, 2016/04/19 15:44:41]

Remove "Literally, "
(seed and general), -> , seed and general,

[mmoroz, 2016/04/19 17:46:36]

Done.

+its output goes into general corpus directory. Seed corpus is read-only.
+
+To upload seed corpus for libFuzzer being run at ClusterFuzz:

[Martin Barbella, 2016/04/19 15:44:41]

for a libFuzzer

[mmoroz, 2016/04/19 17:46:36]

Done.

+
+1) go to [Corpus GCS Bucket]
+
+2) open directory named `%YOUR_FUZZER_NAME%_static`
+
+3) upload corpus files into the directory
+
+
+Alternative way is to use `gsutil` tool:
+```bash
+gsutil -m rsync <corpus_dir_on_disk> gs://clusterfuzz-corpus/libfuzzer/%YOUR_FUZZER_NAME%_static
+```
+
 [Buildbot]: https://goto.google.com/libfuzzer-clusterfuzz-buildbot
 [fuzzer_test.gni]: https://code.google.com/p/chromium/codesearch#chromium/src/testing/libfuzzer/fuzzer_test.gni
 [chromium_libfuzzer.py]: https://code.google.com/p/chromium/codesearch#chromium/build/scripts/slave/recipes/chromium_libfuzzer.py