Make ImageView drawable update more efficient in some cases.

When updating the view's drawable via setImageResource or setImageURI,
make sure to skip the layout pass if the old and new drawable have equal
sizes. This follows what is already done for setDrawable().

Change-Id: If73d225e38d0a2f7c616c4aeb33f67bdaed390f1
Revert "Improve scrolling cache"

This reverts commit 8494d850b517f5c3f5fba50f7117b36daa0cd792.