Fill out implementation of UpdateTestExpectations script

third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/builder_list.py

Index: third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/builder_list.py
diff --git a/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/builder_list.py b/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/builder_list.py
index 617f5874c4b43eeb080369e3de9f5732d8213846..d98979f13979b7ee6647f80a8344b5e1330c8dac 100644
--- a/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/builder_list.py
+++ b/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/builder_list.py
@@ -86,3 +86,11 @@ class BuilderList(object):
                 else:
                     return builder_name
         return debug_builder_name
+
+    def builder_name_for_specifiers(self, version, build_type):

[qyearsley, 2016/07/08 17:55:03]

A docstring here could clarify that version is the OS version specifier (e.g.
"Win7") and build_type is the build configuration type (e.g. "Debug").

[bokan, 2016/07/08 21:12:59]

Done.

+        for builder_name, info in self._builders.items():

[qyearsley, 2016/07/08 17:55:03]

Since dicts are unordered, it's theoretically possible that you could have a
_builders dict like:

    {
        'foo': {'specifiers': ['a', 'b']},
        'bar': {'specifiers': ['a', 'b']},
    }

and then it's not clearly defined whether builder_name_for_specifiers('a', 'b')
should return 'foo' or 'bar'. This likely won't be a problem, but just to make
it clearly defined, you could iterate through `sorted(self._builders.items())`.

[bokan, 2016/07/08 21:12:59]

Done.

+            specifiers = info['specifiers']
+            if specifiers[0].lower() == version.lower() and specifiers[1].lower() == build_type.lower():

[qyearsley, 2016/07/08 17:55:03]

This is implicitly adding an assumption that specifier is always of the form
[<OS version>, <build config>].

I think this is fine, but the comment on line 44 should probably be updated.

[bokan, 2016/07/08 21:12:59]

Done.

+                return builder_name
+
+        return ''