Code review comment for lp:~nick-dedekind/unity/lp1062107.preview-pre-caching

530 + virtual ~PreviewPreCacher();
551 + virtual void OnPreCacheComplete();

Could we make those pure virtual fucntions?

Or if not could we just do:
530 + virtual ~PreviewPreCacher() {}
551 + virtual void OnPreCacheComplete() {}

347 + if (index < 0 || index >=(int)GetResultCount())

Does this need to be casted to an int?

758 + int top_social_info_max_width = MAX(details_width - style.GetAppIconAreaWidth() - style.GetSpaceBetweenIconAndDetails(), 0);
772 + int max_width = MAX(0, geo_cr.width - 2*(geo_cr.width*0.1));
773 + int max_height = MAX(0, (geo_cr.height - TAIL_HEIGHT) - 2*((geo_cr.height - TAIL_HEIGHT)*0.1));
786 + title_->SetMaximumWidth(MAX(0, GetGeometry().width - geo.height - style.GetMusicDurationWidth() - layout_spacing*2));

Lets use std::max() here.