Auto merge of #23516 - pcwalton:webrenderup, r=pcwalton,jdm

Upgrade WebRender

This is against an old Servo because I can't build current Servo due to compile errors in RNG crates. I verified that it starts up.

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<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `___` with appropriate data: -->
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #23516
- [x] There are tests for these changes

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python/tidy/servo_tidy/tidy.py

@@ -371,6 +371,10 @@ def check_lock(file_name, contents):
             source = "crates.io"
         packages_by_name.setdefault(package["name"], []).append((package["version"], source))
 
+    for name in exceptions:
+        if name not in packages_by_name:
+            yield (1, "duplicates are allowed for `{}` but it is not a dependency".format(name))
+
     for (name, packages) in packages_by_name.iteritems():
         has_duplicates = len(packages) > 1
         duplicates_allowed = name in exceptions