Pulling internal changes to github (#3583)

* Internal change.

PiperOrigin-RevId: 187042423

* Internal change.

PiperOrigin-RevId: 187072380

* Opensource float and eight-bit fixed-point mobilenet_v1 training and eval scripts.

PiperOrigin-RevId: 187106140

* Initial check-in for Mobilenet V2

PiperOrigin-RevId: 187213595

* Allow configuring batch normalization decay and epsilon in MobileNet v1

PiperOrigin-RevId: 187425294

* Allow overriding NASNet model HParams.

This is a change to the API that will allow users to pass in their own configs
to the building functions, which should make these APIs much more customizable
for end-user cases.

This change removes the use_aux_head argument from the model construction
functions, which is no longer necessary given that the use_aux_head option is
configurable in the model config. For example, for the mobile ImageNet model,
the auxiliary head can be disabled using:

config = nasnet.mobile_imagenet_config()
config.set_hparam('use_aux_head', 0)
logits, endpoints = nasnet.build_nasnet_mobile(
    inputs, num_classes, config=config)
PiperOrigin-RevId: 188617685

* Automated g4 rollback of changelist 188617685

PiperOrigin-RevId: 188619139

* Removes spurious comment

research/slim/nets/nets_factory.py

@@ -30,6 +30,7 @@ from nets import overfeat
 from nets import resnet_v1
 from nets import resnet_v2
 from nets import vgg
+from nets.mobilenet import mobilenet_v2
 from nets.nasnet import nasnet
 
 slim = tf.contrib.slim
@@ -58,6 +59,7 @@ networks_map = {'alexnet_v2': alexnet.alexnet_v2,
                 'mobilenet_v1_075': mobilenet_v1.mobilenet_v1_075,
                 'mobilenet_v1_050': mobilenet_v1.mobilenet_v1_050,
                 'mobilenet_v1_025': mobilenet_v1.mobilenet_v1_025,
+                'mobilenet_v2': mobilenet_v2.mobilenet,
                 'nasnet_cifar': nasnet.build_nasnet_cifar,
                 'nasnet_mobile': nasnet.build_nasnet_mobile,
                 'nasnet_large': nasnet.build_nasnet_large,
@@ -88,6 +90,7 @@ arg_scopes_map = {'alexnet_v2': alexnet.alexnet_v2_arg_scope,
                   'mobilenet_v1_075': mobilenet_v1.mobilenet_v1_arg_scope,
                   'mobilenet_v1_050': mobilenet_v1.mobilenet_v1_arg_scope,
                   'mobilenet_v1_025': mobilenet_v1.mobilenet_v1_arg_scope,
+                  'mobilenet_v2': mobilenet_v2.training_scope,
                   'nasnet_cifar': nasnet.nasnet_cifar_arg_scope,
                   'nasnet_mobile': nasnet.nasnet_mobile_arg_scope,
                   'nasnet_large': nasnet.nasnet_large_arg_scope,

research/slim/preprocessing/inception_preprocessing.py

@@ -47,7 +47,7 @@ def distort_color(image, color_ordering=0, fast_mode=True, scope=None):
 
   Each color distortion is non-commutative and thus ordering of the color ops
   matters. Ideally we would randomly permute the ordering of the color ops.
-  Rather than adding that level of complication, we select a distinct ordering
+  Rather then adding that level of complication, we select a distinct ordering
   of color ops for each preprocessing thread.
 
   Args: