This folder contains code to support W3C Encrypted Media Extensions (EME), key systems and Content Decryption Modules (CDM). It's under //components folder so they can be shared by multiple embedders of content, e.g. //chrome and //android_webview. See //components use cases for more context.
This means that only content embedders can depend on targets in this folder, including //chrome, //chromecast, //android_webview, //fuchsia_web, and //content/shell (test content embedder). Other folders, especially //media and //content, should NOT depend on targets in this folder.
In general, key system specific logic should not be in //media or //content. So it's also a good practice to put them under //components/cdm.