Add the run tests in iframe feature.

[xiuqijix]

This change is 

[hoppipolla-critic-bot]

Critic review: https://critic.hoppipolla.co.uk/r/5789

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[xiuqijix]

Add a feature that run tests in iframe by select "Run Tests in "iframe"" checkbox.

[jgraham]

Just the top patch here has a handful of trivial issues (see critic) and I would like to merge it if you fix those.

[yugang]

@jgraham , the first two commits have the same reason here: #31, we just need merge the last one of the four commits.

[xiuqijix]

@jgraham , the first three commits have the same reason here: #32 .You can merge #33 after #32 , thanks.