Fetch retry summary and use it to determine what tests to rebaseline.

third_party/WebKit/Tools/Scripts/webkitpy/common/net/buildbot_mock.py

Index: third_party/WebKit/Tools/Scripts/webkitpy/common/net/buildbot_mock.py
diff --git a/third_party/WebKit/Tools/Scripts/webkitpy/common/net/buildbot_mock.py b/third_party/WebKit/Tools/Scripts/webkitpy/common/net/buildbot_mock.py
index 2ffdcfc8d029709f58d4ba8dce0e2a9ee75461c6..4239b624b4855b2982f7d167b128184b91717b41 100644
--- a/third_party/WebKit/Tools/Scripts/webkitpy/common/net/buildbot_mock.py
+++ b/third_party/WebKit/Tools/Scripts/webkitpy/common/net/buildbot_mock.py
@@ -40,6 +40,7 @@ class MockBuildBot(BuildBot):
         super(MockBuildBot, self).__init__()
         # Dict of Build to canned LayoutTestResults.
         self._canned_results = {}
+        self._canned_retry_summary_json = {}
 
     def fetch_layout_test_results(self, _):
         return LayoutTestResults.results_from_string(LayoutTestResultsTest.example_full_results_json)
@@ -51,3 +52,9 @@ class MockBuildBot(BuildBot):
         return self._canned_results.get(
             build,
             LayoutTestResults.results_from_string(LayoutTestResultsTest.example_full_results_json))
+
+    def set_retry_sumary_json(self, build, content):
+        self._canned_retry_summary_json[build] = content
+
+    def fetch_retry_summary_json(self, build):
+        return self._canned_retry_summary_json.get(build)