rebaseline.py: keep going if we encounter an "INVALID" entry in the JSON file

Review URL: https://codereview.chromium.org/16826003

git-svn-id: http://skia.googlecode.com/svn/trunk@9543 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tools/rebaseline.py b/tools/rebaseline.py
index 157d8c2..e270e90 100755
--- a/tools/rebaseline.py
+++ b/tools/rebaseline.py
@@ -140,6 +140,10 @@
             print ('# unable to find filename %s in all_results dict' %
                    infilename)
             return False
+        except ValueError as e:
+            print '# ValueError reading filename %s from all_results dict: %s'%(
+                infilename, e)
+            return False
         url = '%s/%s/%s/%s.png' % (self._googlestorage_gm_actuals_root,
                                    hash_type, test_name, hash_value)
         try: