Hide #contentSub properly

It is treated specially which results in it being set to opacity=0 instead
of hidden, and leaves a large space at the top of the document. Removing
special treatment of it results in it being hidden properly.

Bug: 52243
Bug: 54325
Change-Id: I2d6157708bd7b4c3a7c6474b1612862120f963b7
Merge "Hide #contentSub properly"