Implement chrome.downloads.onDeterminingFilename()

chrome/common/extensions/api/downloads.idl

Index: chrome/common/extensions/api/downloads.idl
diff --git a/chrome/common/extensions/api/downloads.idl b/chrome/common/extensions/api/downloads.idl
index 3481229557c8b584baa89938e798e6907fc71110..0c8842e86334b2d79faad5f6fc16df546249cd46 100644
--- a/chrome/common/extensions/api/downloads.idl
+++ b/chrome/common/extensions/api/downloads.idl
@@ -12,6 +12,16 @@ namespace downloads {
     DOMString value;
   };
 
+  // $ref:onDeterminingFilename handlers may return a FilenameDetermination
+  // object in order to override a download's target filename.
+  dictionary FilenameDetermination {
+    // The download's new target filename.
+    DOMString? filename;
+
+    // Whether to overwrite any existing files.
+    boolean? overwrite;
+  };
+
   [inline_doc] enum HttpMethod {GET, POST};
 
   [inline_doc] dictionary DownloadOptions {
@@ -376,9 +386,6 @@ namespace downloads {
     // then <code>callback</code> will be called.
     static void erase(DownloadQuery query, optional EraseCallback callback);
 
-    // TODO(benjhayden) Comment.
-    [nodoc] static void setDestination(long downloadId, DOMString relativePath);
-
     // Prompt the user to either accept or cancel a dangerous download.
     // <code>acceptDanger()</code> does not automatically accept dangerous
     // downloads.
@@ -402,5 +409,12 @@ namespace downloads {
     // except <code>bytesReceived</code> changes, this event fires with the
     // <code>downloadId</code> and an object containing the properties that changed.
     static void onChanged(DownloadDelta downloadDelta);
+
+    // During the filename determination process, extensions will be given the
+    // opportunity to override the target filename. Handlers may return null in
+    // order to allow the target filename to be used, or return a
+    // $ref:FilenameDetermination object in order to override the target
+    // filename.
+    static void onDeterminingFilename(DownloadItem downloadItem);
   };
 };