Declare providing extension capabilities in the manifest.

chrome/common/extensions/api/file_system_provider.idl

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Use the <code>chrome.fileSystemProvider</code> API to create file systems,
 // that can be accessible from the file manager on Chrome OS.
 [implemented_in="chrome/browser/chromeos/extensions/file_system_provider/file_system_provider_api.h"]
 namespace fileSystemProvider {
   // Error codes used by providing extensions in response to requests as well
   // as in case of errors when calling methods of the API. For success, <code>
@@ skipping 23 matching lines @@
     READ,
     WRITE
   };
 
   // Type of a change detected on the observed directory.
   enum ChangeType {
     CHANGED,
     DELETED
   };
 
-  // Source of the file system data.
-  enum FileSystemSource {
-    // The file system is handling a file, eg. an archive file obtained via the
+  // Source of data for provided file systems. Used in manifest files of
+  // providing extensions.
+  enum Source {
+    // File systems are handling files, eg. an archive file obtained via the
     // <code>onLaunched</code> event and the <code>file_handlers</code> manifest
     // entry.
-    FILE,
+    file,
 
-    // The file system contents are fetched from an external device, such as a
+    // File systems' contents are fetched from an external device, such as a
     // USB device, but not via <code>file_handlers</code>.
-    DEVICE,
+    device,
 
-    // The file system is network based. The contents are obtained from another
+    // File systems are network based. The contents are obtained from another
     // server or local network. Eg. cloud services.
-    NETWORK
+    network
+  };
+
+  // Represents capabilities of a providing extension. Used in manifest files of
+  // providing extensions.
+  dictionary Capabilities {
+    // Whether configuring via <code>onConfigureRequested</code> is supported.
+    boolean configurable;
+
+    // Whether multiple (more than one) mounted file systems are supported.
+    boolean multiple_mounts;

[not at google - send to devlin, 2015/04/23 23:16:35]

multipleMounts would be more consistent.

[mtomasz, 2015/04/24 12:16:11]

In manifest we always use underscored_keys. So we either have consistency within
manifest, or consistency with results of
fileBrowserPrivate.getProvidingExtensions(). Which one do you prefer?

[not at google - send to devlin, 2015/04/24 16:18:32]

There are plenty of counterexamples to this rule, but for better or worse, we
typically use underscores for manifest keys and camelcase for APIs. It should
really be camelcase for everything.

For an example of something where we differ in manifest and the API, see the
browser action API; the manifest keys are browser_action,
browser_action.default_title, etc; but the API uses browserAction,
browserAction.setTitle, browserAction.setTitle({imageData}), etc.

[mtomasz, 2015/04/24 17:12:10]

Well, this is exactly what I'm doing. This dictionary is used for manifest
parsing (see comment). For extensions, on JS side, camelCase is used instead,
see file_manager_private.idl.

+
+    // Source of data for all mounted file systems.
+    Source source;

[not at google - send to devlin, 2015/04/23 23:16:35]

This is now required; was that an intentional change? should there be, or does
there need to be, an "other" in the source?

[mtomasz, 2015/04/24 12:16:11]

I found the "OTHER" an overkill. Instead I decided to use a default "FILE" if
the entire "file_system_provider" section is not available. The manifest section
is optional, but all keys required if the section is declared.

   };
 
   // Represents metadata of a file or a directory.
   dictionary EntryMetadata {
     // True if it is a directory.
     boolean isDirectory;
 
     // Name of this entry (not full path name). Must not contain '/'. For root
     // it must be empty.
     DOMString name;
@@ skipping 50 matching lines @@
     // of the file system (such as creating, deleting or writing to files).
     boolean writable;
 
     // The maximum number of files that can be opened at once. If 0, then not
     // limited.
     long openedFilesLimit;
 
     // List of currently opened files.
     OpenedFile[] openedFiles;
 
-    // Source of the file system data.
-    FileSystemSource? source;
-
     // Whether the file system supports the <code>tag</code> field for observing
     // directories.
     [nodoc] boolean? supportsNotifyTag;
 
     // List of watchers.
     [nodoc] Watcher[] watchers;
   };
 
   // Options for the <code>mount()</code> method.
   dictionary MountOptions {
     // The string indentifier of the file system. Must be unique per each
     // extension.
     DOMString fileSystemId;
 
     // A human-readable name for the file system. 
     DOMString displayName;
 
     // Whether the file system supports operations which may change contents
     // of the file system (such as creating, deleting or writing to files).
     boolean? writable;
 
     // The maximum number of files that can be opened at once. If not specified,
     // or 0, then not limited.
     long? openedFilesLimit;
 
-    // Source of the file system data.
-    FileSystemSource? source;
-
     // Whether the file system supports the <code>tag</code> field for observed
     // directories. Required in order to enable the internal cache.
     [nodoc] boolean? supportsNotifyTag;
   };
 
   // Options for the <code>unmount()</code> method.
   dictionary UnmountOptions {
     // The identifier of the file system to be unmounted.
     DOMString fileSystemId;
   };
@@ skipping 513 matching lines @@
 
     // Raised when the watcher should be removed. If an error occurs, then
     // <code>errorCallback</code> must be called.
     [maxListeners=1, nodoc] static void onRemoveWatcherRequested(
       RemoveWatcherRequestedOptions options,
       ProviderSuccessCallback successCallback,
       ProviderErrorCallback errorCallback);
   };
 };