Allow the IPC fuzzer to use a platform-specific corpus.

tools/ipc_fuzzer/scripts/ipc_fuzzer_mut.py

Index: tools/ipc_fuzzer/scripts/ipc_fuzzer_mut.py
diff --git a/tools/ipc_fuzzer/scripts/ipc_fuzzer_mut.py b/tools/ipc_fuzzer/scripts/ipc_fuzzer_mut.py
index 595caf1f9f2dd53e9472dd19492856f04235847a..98011c09103b977b6bf4962b87c581a78a0c6843 100755
--- a/tools/ipc_fuzzer/scripts/ipc_fuzzer_mut.py
+++ b/tools/ipc_fuzzer/scripts/ipc_fuzzer_mut.py
@@ -41,8 +41,16 @@ class MutationalFuzzer:
         chrome_application_directory, self.ipc_replay_binary)
 
   def set_corpus(self):
-    input_directory = self.args.input_dir
-    entries = os.listdir(input_directory)
+    # Corpus should be set per job as a fuzzer-specific environment variable.
+    try:
+      corpus = os.environ['CORPUS']

[inferno, 2015/05/11 21:22:43]

os.getenv('CORPUS', 'default') is better here. no need of try-except. Also,
maybe s/CORPUS/CORPUS_DIR

+    except KeyError:
+      corpus = 'default'
+    corpus_directory = os.path.join(self.args.input_dir, corpus)

[inferno, 2015/05/11 21:22:43]

new-line before this line.

+    if not os.path.exists(corpus_directory):
+      sys.exit('Corpus directory "%s" not found.' % corpus_directory)
+
+    entries = os.listdir(corpus_directory)
     entries = [i for i in entries if i.endswith(utils.IPCDUMP_EXTENSION)]
     self.corpus = [os.path.join(input_directory, entry) for entry in entries]