Support choosing multiple files with fileSystem.chooseEntry.

chrome/common/extensions/api/file_system.idl

Index: chrome/common/extensions/api/file_system.idl
diff --git a/chrome/common/extensions/api/file_system.idl b/chrome/common/extensions/api/file_system.idl
index e2bd173f71670d2259a17e6bf59a70499d650257..9aec015491efd1eef3a1809014a723f4f04b1fff 100644
--- a/chrome/common/extensions/api/file_system.idl
+++ b/chrome/common/extensions/api/file_system.idl
@@ -55,9 +55,18 @@ namespace fileSystem {
     // in the accepts argument. The default is true. If the accepts field is
     // unset or contains no valid entries, this will always be reset to true.
     boolean? acceptsAllTypes;
+
+    // Whether to accept multiple files. This is only supported for openFile and
+    // openWritableFile. The callback to chooseEntry will be called with a list
+    // of entries if this is set to true. Otherwise it will be called with a
+    // single Entry.
+    boolean? acceptsMultiple;
   };
   callback GetDisplayPathCallback = void (DOMString displayPath);
   callback FileEntryCallback = void ([instanceOf=FileEntry] object fileEntry);
+  callback MultipleFileEntryCallback = void (
+      [instanceOf=FileEntry] optional object fileEntry,

[Matt Giuca, 2013/07/19 02:28:11]

What is the first fileEntry for? (Why not just take a list?) If there is a good
reason, please document.

[Sam McNally, 2013/07/19 04:22:14]

Backwards compatibility; chooseEntry with acceptsMultiple: false returns a
single FileEntry. The callback needs to accept one FileEntry or FileEntry[] and
this syntax doesn't make the parser angry. A comment here would end up in the
docs.

[Matt Giuca, 2013/07/25 08:31:09]

Is it worth refactoring so that there are two separate interfaces for opening a
dialog (single and multiple); the single one returns FileEntryCallback and the
multiple one returns MultipleFileEntryCallback? It seems messy this way. Will
the user see the name "OneOrMultipleFileEntryCallback" (even in the
documentation) or is that hidden?

[benwells, 2013/07/25 09:08:31]

Do you mean there would be another function like chooseEntries (or
chooseMultipleEntries) which is identical except it implies multiple entries and
has an array in the callback?

That would work; I'm not sure if it is better. My vote would be to leave it as
is but rename the type to FileEntriesCallback (or something). We can explain in
doco how to use it. I'd weigh the vote of someone with more javascript
experience more than mine though; I was under the impression this kind of type
shenanigans are common in JS.

[Sam McNally, 2013/07/26 03:58:03]

Done.

+      [instanceOf=FileEntry] optional object[] fileEntries);
   callback IsWritableCallback = void (boolean isWritable);
   callback IsRestorableCallback = void (boolean isRestorable);
 
@@ -79,7 +88,7 @@ namespace fileSystem {
 
     // Ask the user to choose a file.
     static void chooseEntry(optional ChooseEntryOptions options,
-                            FileEntryCallback callback);
+                            MultipleFileEntryCallback callback);
 
     // Returns the file entry with the given id if it can be restored. This call
     // will fail otherwise.