Declare providing extension capabilities in the manifest.

chrome/common/extensions/api/manifest_types.json

Index: chrome/common/extensions/api/manifest_types.json
diff --git a/chrome/common/extensions/api/manifest_types.json b/chrome/common/extensions/api/manifest_types.json
index ca479fbbfd9b074f4fb5c66a4ceaa8c568b0f4ab..37abb295dce27d1a6f0999b04b675ccd045d58fb 100644
--- a/chrome/common/extensions/api/manifest_types.json
+++ b/chrome/common/extensions/api/manifest_types.json
@@ -168,6 +168,32 @@
             }
           }
         ]
+      },
+      {
+        "id": "FileSystemProviderSource",
+        "type": "string",
+        "description": "For <code>file</code> the source is a file passed via <code>onLaunched</code> event. For <code>device</code> contents are fetched from an external device (eg. plugged via USB), without using <code>file_handlers</code>. Finally, for <code>device</code> source, contents should be fetched via network.",
+        "enum": ["file", "device", "network"]
+      },
+      {
+        "id": "FileSystemProviderCapabilities",
+        "description": "Represents capabilities of a providing extension.",
+        "optional": true,
+        "type": "object",
+        "properties": {
+          "configurable": {
+            "type": "boolean",
+            "description": "Whether configuring via <code>onConfigureRequested</code> is supported."
+          },
+          "multiple_mounts": {
+            "type": "boolean",
+            "description": "Whether multiple (more than one) mounted file systems are supported."
+          },
+          "source": {
+            "$ref": "FileSystemProviderSource",
+            "description": "Source of data for mounted file systems."
+          }
+        }
       }
     ]
   }