Let UpSampling2D Layer accept undetermined image sizes

[caisq]

Fixes: tensorflow/tfjs#403

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This change is 

[caisq]

cc @oeway

[bileschi]

Reviewable status: 0 of 1 LGTMs obtained

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src/layers/convolutional_test.ts, line 1114 at r2 (raw file):

'undetermined image size'

Possibly a better test name here is in order. Something like: Layer is reusable for multiple sizes. -- Concrete tensors can not have undetermined size, and the first half of this test is identical to 'channelsLast' above.

[bileschi]

Reviewable status: complete! 1 of 1 LGTMs obtained

[caisq]

Reviewable status: complete! 1 of 1 LGTMs obtained

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src/layers/convolutional_test.ts, line 1114 at r2 (raw file):

Previously, bileschi (Stanley Bileschi) wrote…

'undetermined image size'

Possibly a better test name here is in order. Something like: Layer is reusable for multiple sizes. -- Concrete tensors can not have undetermined size, and the first half of this test is identical to 'channelsLast' above.

Thanks. Renamed the test to "varying input image sizes"