VarianceScaling initializer: Fix default arg values

[caisq]

• The VarianceScaling initializer is the base class of initializers
  such as GlorotNormal, HeNormal and LeCunNormal. But in relatively
  rare occasions, it is used by itself.
• Previously, the default values of the mode and distribution
  were not set properly, leading to inconsistent behavior with keras.
  This CL fixes that.

Re tensorflow/tfjs#1434

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This change is 

[davidsoergel]

Reviewable status: 0 of 1 approvals obtained (waiting on @caisq and @davidsoergel)

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src/initializers.ts, line 329 at r1 (raw file):

  /** Fanning mode for inputs and outputs. */
  mode: FanMode;

Should these be mode? and distribution? now that you provide defaults?

And, assuming yes, can you update the keras_format VarianceScalingConfig also?

[caisq]

Reviewable status: 0 of 1 approvals obtained (waiting on @davidsoergel)

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src/initializers.ts, line 329 at r1 (raw file):

Previously, davidsoergel (David Soergel) wrote…

Should these be mode? and distribution? now that you provide defaults?

And, assuming yes, can you update the keras_format VarianceScalingConfig also?

Yep. Done.

[davidsoergel]

Reviewed 1 of 2 files at r1, 2 of 2 files at r2.
Reviewable status: complete! 1 of 1 approvals obtained (waiting on @davidsoergel)