Revert "Cleanup webviews when we no longer require them"

Was causing crashes when back button was pressed. Needs
a better longer term memory management solution instead.

This reverts commit 488bece3e5fd6985822ec7b404ade1cf16f3bc36.

Change-Id: I54503cac5640eeaaf3e5658ae3b2bbe35175dac0
Merge "Revert "Cleanup webviews when we no longer require them""