Add a data source field for volumes.

chrome/common/extensions/api/file_system_provider.idl

Index: chrome/common/extensions/api/file_system_provider.idl
diff --git a/chrome/common/extensions/api/file_system_provider.idl b/chrome/common/extensions/api/file_system_provider.idl
index 2854ae84e3673d7a81fc3883f8fb4a24915746c5..ad9b9dc37fdb469758dcd8bf10d50bdc5359ce3a 100644
--- a/chrome/common/extensions/api/file_system_provider.idl
+++ b/chrome/common/extensions/api/file_system_provider.idl
@@ -41,6 +41,22 @@ namespace fileSystemProvider {
     DELETED
   };
 
+  // Source of the file system data.
+  enum FileSystemSource {
+    // The file system is handling a file, eg. an archive file obtained via the
+    // <code>OnLaunched</code> event and the <code>file_handlers</code> manifest
+    // entry.
+    FILE,
+
+    // The file system contents are provided fetched from a device, such as a
+    // USB device.

[hirono, 2015/04/06 08:36:34]

nit: please note downloads's source is device.

[mtomasz, 2015/04/06 09:13:48]

Done in file_manager_private.idl.

+    DEVICE,
+
+    // The file system is network based. The contents are obtained from another
+    // server or local network. Eg. cloud services.
+    NETWORK
+  };
+
   // Represents metadata of a file or a directory.
   dictionary EntryMetadata {
     // True if it is a directory.
@@ -109,6 +125,9 @@ namespace fileSystemProvider {
     // 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;
@@ -134,6 +153,9 @@ namespace fileSystemProvider {
     // 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;
@@ -451,6 +473,9 @@ namespace fileSystemProvider {
     // must be descriptive but doesn't have to be unique. The <code>fileSystemId
     // </code> must not be an empty string.
     //
+    // Depending on the type of the file system being mounted, the <code>source
+    // </code> option must be set apprioprietly. 
+    //
     // In case of an error, <code>chrome.runtime.lastError</code> will be set
     // will a corresponding error code.
     static void mount(MountOptions options,