What are these white areas of coronary thrombosis?
Low density lipoproteins can be taken up by the macrophages under a number of circumstances (typically high circulating levels is the most important). These macrophages are called foam cells. The macrophage can then die and deposit this cholesterol and fatty material onto a vessel wall in the context of atherosclerosis. Additionally tissue damage as a result of release of damaging chemicals from the macrophage can induce an inflammatory response recruiting more macrophages (worsening the problem in a cyclical manner) and result in fibrosis and platelet activation. I think this would cause the white stuff you point to. 

In summary I think you're right, it's a combination of fat, cholesterol, fibrotic tissue and platelets. 3 is more likely macrophages and platelets whilst 1 and 2 are more likely a combination of all the above.