Well, that' pretty much says it. In the new Yosemite Photos I can drag & drop pictures inside the OS, but they won't drag and drop to a web browser (safari, chrome, or firefox). I do this pretty frequently (gmail, facebook messages, wordpress). Thought I would put this out there in the world, don't really expect anyone to have a fix 😟
See TD's user Tip. How to Access Files in iPhoto
It explainxs the different ways to access photos in a photo library from differnet applications.
The Media Browser is a central service in MacOS to give other appications access to media libraries - videos, photos, music. In some applications it is called photo browser.
The Media Browser, is available in the "File > Open" dialog in compatible applications. Scroll down in the sidebar of the File > Open dialog panel to "Media" as described by Larry. Some older applications cannot support it, if they have not yet been updated for a full compatibility with El Capitan.
Photos: Can't Drag & Drop to Browser
