• Motivation for features / changes
  There is a bug where the lines on the histogram chart do not align with the ticks in the YAxis. This because of some fault logic around the maximum number ticks to be shown there. The issue will occur when the number of lines (steps) is fewer than the height of the chart / 15 (a seemingly arbitrary value).

• Technical description of changes
  I updated the logic surrounding the number of ticks to be shown so that the number of ticks <= number steps.

• Screenshots of UI changes
  Before
  
  

After

• Detailed steps to verify changes work correctly (as executed by you)

1. Start tensorboard with a log directory containing histogram data. Below is some python code. which should generate valid logs.
2. Navigate to localhost:6006?enableDataTable&enableLinkedTime
3. Note that the histogram chart has the same number of YAxis ticks as lines on the chart.
4. Enable linked time and set a value for the upper value to enable range selection.
   
5. Note that the upper fob is placed correctly on the chart.

# https://www.tensorflow.org/tensorboard/get_started
import tensorflow as tf
import datetime
mnist = tf.keras.datasets.mnist

(x_train, y_train),(x_test, y_test) = mnist.load_data()
x_train, x_test = x_train / 255.0, x_test / 255.0

def create_model():
  return tf.keras.models.Sequential([
    tf.keras.layers.Flatten(input_shape=(28, 28)),
    tf.keras.layers.Dense(512, activation='relu'),
    tf.keras.layers.Dropout(0.2),
    tf.keras.layers.Dense(10, activation='softmax')
  ])

model = create_model()
model.compile(optimizer='adam',
              loss='sparse_categorical_crossentropy',
              metrics=['accuracy'])

log_dir = "logs/fit/" + datetime.datetime.now().strftime("%Y%m%d-%H%M%S")
tensorboard_callback = tf.keras.callbacks.TensorBoard(log_dir=log_dir, histogram_freq=1)

model.fit(x=x_train, 
          y=y_train, 
          epochs=5, 
          validation_data=(x_test, y_test), 
          callbacks=[tensorboard_callback])

• Alternate designs / implementations considered