Make image dashboard sizing slightly nicer
Make image dashboard sizing slightly nicer

This change causes the image size to start out at 300x300. Then once we
fetch all the image metadata for a row, the heights will be scaled down
based on the aspect ratio and the row height will change accordingly.

When the images are reloaded sixty seconds later, the page contents will
not reflow. However the images will disappear while they're loading.
That will be fixed next.
Change: 131198628

francoisluus/tensorboard-supervise,qiuminxu/tensorboard,tensorflow/tensorboard,qiuminxu/tensorboard,agrubb/tensorboard,shakedel/tensorboard,agrubb/tensorboard,francoisluus/tensorboard-supervise,francoisluus/tensorboard-supervise,qiuminxu/tensorboard,tensorflow/tensorboard,tensorflow/tensorboard,tensorflow/tensorboard,ioeric/tensorboard,ioeric/tensorboard,agrubb/tensorboard,ioeric/tensorboard,qiuminxu/tensorboard,shakedel/tensorboard,tensorflow/tensorboard,francoisluus/tensorboard-supervise,shakedel/tensorboard,francoisluus/tensorboard-supervise,agrubb/tensorboard,qiuminxu/tensorboard,tensorflow/tensorboard,ioeric/tensorboard,shakedel/tensorboard,qiuminxu/tensorboard,shakedel/tensorboard,francoisluus/tensorboard-supervise,shakedel/tensorboard,agrubb/tensorboard,agrubb/tensorboard,ioeric/tensorboard,tensorflow/tensorboard,ioeric/tensorboard