Cleaned up garbage collection.

Removed garbage collection related Register/UnRegister/
ReportReferences calls from classes that did not need them.
Using garbage collection unnecessarily can lead to
performance issues.

Change-Id: I2eefb6a86d9e64f898247df522a6082c07cec8aa
Merge topic 'garbage-collection-cleanup' into master

0e39fa5d Cleaned up garbage collection.