[libwebp] enable dataflow config (#1632). (#3271)

* [libwebp] enable dataflow config (#1632).

Tested as https://pantheon.corp.google.com/logs/viewer?resource=build%2Fbuild_id%2F8b9c16ef-8238-44c1-817c-03602fff5583&project=oss-fuzz&minLogLevel=0&expandAll=false&timestamp=2020-01-21T23:43:43.816000000Z&customFacets=&limitCustomFacetWidth=true&dateRangeEnd=2020-01-21T23:43:11.054Z&interval=PT1H&dateRangeUnbound=backwardInTime&scrollTimestamp=2020-01-21T19:46:16.396688731Z

* Update project.yaml

projects/libwebp/project.yaml

@@ -1,14 +1,20 @@
 homepage: "https://developers.google.com/speed/webp/"
 primary_contact: "jzern@google.com"
+fuzzing_engines:
+  - libfuzzer
+  - afl
+  - honggfuzz
+  - dataflow
 sanitizers:
-- address
-- undefined
-- memory
+  - address
+  - undefined
+  - memory
+  - dataflow
 auto_ccs:
-- pascal.massimino@gmail.com
-- vrabaud@google.com
-- yguyon@google.com
+  - pascal.massimino@gmail.com
+  - vrabaud@google.com
+  - yguyon@google.com
 vendor_ccs:
-- aosmond@mozilla.com
-- tnikkel@mozilla.com
-- twsmith@mozilla.com
+  - aosmond@mozilla.com
+  - tnikkel@mozilla.com
+  - twsmith@mozilla.com