NEW_MULTISYMBOL: make experiment depend on EC_ADAPT.
NEW_MULTISYMBOL: make experiment depend on EC_ADAPT.

Simplify the number of different compile and code paths.

Change-Id: Id5b061571daeb070b91ec762fe7e07e8c114229e

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