Commits
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7346896 Changed Serialized#supportsNormalization to PRIVATE
e851efc Updated SerializerTest with "normalizeTraversable" & "testNormalizeGivesPriorityToInterfaceOverTraversable"
d789f94 Serializer#normalize gives precedence to objects that support normalization
9e6ba9a Added protected Serializer#supportsNormalization
Discussion
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[Serializer] `normalize` should use supported normalizer before Traversable
Bug fix: yes
Feature addition: no
Backwards compatibility break: no (discussion needed)
Symfony2 tests pass: yes
Fixes the following tickets: #2295
**Same as PR #2539, except rebased onto `2.0`**
Should I abstract out a `supportsDenormalization` function just for symmetry?