Summary:
The following types can be encoded and decoded by the json library:
`dict`, `list`, `tuple`, `str`, `unicode`, `int`, `long`, `float`, `bool`, `NoneType`.
`JSONMetricValue` can be constructed with any of these types, and used as part of Test.Result.
This patch also adds a toMetricValue function that converts a value into a MetricValue.
Reviewers: ddunbar, EricWF
Reviewed By: EricWF
Subscribers: cfe-commits, llvm-commits
Differential Revision: http://reviews.llvm.org/D6576
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224628 91177308-0d34-0410-b5e6-96231b3b80d8
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