The Beginnings of Chocolate: Not French
To quickly race through a few hundred years of history, chocolate is derived from cacao, which was first discovered by Europeans in Central and South America. Since that was an area of the "New World" dominated by the Spanish and by Portugal, chocolate entered Europe through those countries. In France, many of the first documented mentions of chocolate referred to it as either Spanish or Mexican.
Eventually, France would colonize Martinique and import its cacao, but its quality was not considered to be as good as the cacao brought in through Spain and Portugal. (And this sentiment was attributed to none other than Antoine Gallais, of the first chocolate shop in Paris, Debauve & Gallais.)
Chocolate's Development: Still Not French
Given that it was a costly import, chocolate was a luxury item in France throughout the 17th century—mostly an upper-class beverage, although also sometimes used medicinally. Chocolate was not quite elevated to the status of food— heading into the 19th century the royal right to sell chocolate was reserved to limonadiers , or coffee houses, and apothecaries. In fact, Suplice Debauve, the other founder of Debauve & Gallais, was a pharmacist.
Perhaps this is why most of the important developments in chocolate which led to its mass-production and consumption occurred outside of France: separation of cocoa bean from butter was invented by Coenraad Johannes van Houton (Dutch); it was Henri Nestle (German) who invented powdered milk which led to the development of milk chocolate by Daniel Peter (Swiss). Rodolphe Lindt, also Swiss, developed chocolate conching, which led to production of fondant in 1879.
Heading into the modern era, while there were many small artisanal French chocolatiers, Belgian imports started to account for an important part of the French market. (Belgium's chocolates are thought to be sweeter, richer and larger than French chocolates.)
Chocolate Today: The French ArriveIn recent times, French chocolatiers have banded together to reclaim chocolate as part of the French "culinary patrimony". The Académie Française du Chocolat et de la Confiserie was founded in 1998, for example -- with a similar mission that the Académie Française has to preserving and protecting the French language.
There are many fine chocolatiers working in France and in Paris today. But still, in terms of sweets and treats, the French reputation is the longest for pastries—canneles from Bordeaux, for instance—and for candies made from a sugar or a sugar-nut base, such as nougat, marron glace, and so on.
But there is one chocolate development that can definitely be put on the French scoreboard: the delightful combination of pastry and chocolate, in the form of éclairs, of course, but also in the brilliant idea of eating chocolate for breakfast. From 1715-1723 Philippe d'Orleans, regent for Louis XV, held court over chocolate at breakfast.
Note: In this essay, I've relied on the excellent Chocolate: History, Culture, Heritage, particularly Bertram M. Gordon's essay "Chocolate in France: Evolution of a Luxury Product", and Crafting the Culture and History of French Chocolate by Susan J. Terrio.