Multiple regressions in display of charts in scalars tab.

Environment information (required)

Please run diagnose_tensorboard.py (link below) in the same
environment from which you normally run TensorFlow/TensorBoard, and
paste the output here:

Run on Google's internal infrastructure using latest prebuilt tensorboard binaries.

For browser-related issues, please additionally specify:

• Browser type and version: Chrome 76.0.3809.100 (Official Build) (64-bit)
• Screenshot, if it’s a visual issue:

Issue description

About a week ago, multiple regressions appeared in the scalars tab. One such regression is shown in the attached screenshot. This occurs intermittently when refreshing with the tensorboard refresh button.

Another regression is that, when refreshing, charts often fail to automatically expand their x dimension to accommodate new data.

Another regression is that closing and reopening a particular panel of charts used to refresh the charts. Now the charts remain cached across panel closes. This removed the easiest way to fix situations where multiple charts had been zoomed or panned, or were not updating correctly. Instead, the only way I have found to reset the charts (besides a full page reload) is by entering a random value into the Runs regex field such that no runs are selected, and then clearing out that value. This is much less convenient than just closing and reopening the problematic panel.

Reproduce the reported behavior in TensorBoard's Scalars tab using the refresh button, including the screenshot's chart regression, failure to expand the x dimension, and cached panels after closing and reopening. Trace the chart refresh and panel lifecycle behavior from the Scalars tab entry point; done means refreshed charts update, resize for new data, and reset when their panel is reopened.