If your pup ate 150g of chocolate that is about 5.3 oz. I found this information on a website:
On average,
Milk chocolate contains 44 mg of theobromine per oz.
Semisweet chocolate contains 150mg/oz.
Baker's chocolate 390mg/oz.
Using a dose of 100 mg/kg as the toxic dose it comes out roughly as:
1 ounce per 1 pound of body weight for Milk chocolate
1 ounce per 3 pounds of body weight for Semisweet chocolate
1 ounce per 9 pounds of body weight for Baker's chocolate.
Also, I think these chocolates are filled with something? If so, that means it's not 5.3 oz of pure chocolate. Even if it was baker's chocolate, (which I highly doubt), and pure chocolate, 9 pounds of body weight per ounce would equal about 50 pounds, which means your pup should be ok. There may be some diarrhea, but other than that he should be ok. Definitely make sure he stays hydrated.
I would still call the vet maybe, just to ease your mind. After all, I'm just some random girl on the internet that doesn't have the greatest math skills.