An empty .results file would throw ValueError, eat it.

tools/isolate/isolate_smoke_test.py

Index: tools/isolate/isolate_smoke_test.py
diff --git a/tools/isolate/isolate_smoke_test.py b/tools/isolate/isolate_smoke_test.py
index 02ad18c32bcf129c8697a785e329d2ee2d3b752c..a11d17f5f3cabc5270a8d97c6fd307bad794aee9 100755
--- a/tools/isolate/isolate_smoke_test.py
+++ b/tools/isolate/isolate_smoke_test.py
@@ -478,7 +478,11 @@ class Isolate_trace(IsolateBase):
       # Includes spew from tracerpt.exe.
       self.assertTrue(out.startswith(expected))
     else:
-      self.assertEquals(expected, out.rstrip())
+      lines = out.strip().splitlines()
+      self.assertEquals(3, len(lines))
+      self.assertTrue(lines[0].startswith('WARNING'))
+      self.assertTrue(lines[1].startswith('WARNING'))
+      self.assertEquals(expected, lines[2])
 
   def test_missing_trailing_slash(self):
     try: