Add test code for optimize_txb()
Add test code for optimize_txb()

Change-Id: Ieae4c1a1c932d375b4577c7e42a9764e5f9cd16a

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom