Implement 'drop-files' tray event on OS X.

atom/browser/ui/tray_icon_cocoa.mm

@@ -41,6 +41,8 @@ const CGFloat kMargin = 3;
                             kStatusItemLength,
                             [[statusItem_ statusBar] thickness]);
   if ((self = [super initWithFrame:frame])) {
+    [self registerForDraggedTypes:
+        [NSArray arrayWithObjects:NSFilenamesPboardType, nil]];
     [statusItem_ setView:self];
   }
   return self;
@@ -174,6 +176,24 @@ const CGFloat kMargin = 3;
   trayIcon_->NotifyRightClicked([self getBoundsFromEvent:event]);
 }
 
+- (NSDragOperation)draggingEntered:(id <NSDraggingInfo>)sender {
+  return NSDragOperationCopy;
+}
+
+- (BOOL)performDragOperation:(id <NSDraggingInfo>)sender {
+  NSPasteboard* pboard = [sender draggingPasteboard];
+
+  if ([[pboard types] containsObject:NSFilenamesPboardType]) {
+    std::vector<std::string> dropFiles;
+    NSArray* files = [pboard propertyListForType:NSFilenamesPboardType];
+    for (NSString* file in files)
+      dropFiles.push_back(base::SysNSStringToUTF8(file));
+    trayIcon_->NotfiyDropFiles(dropFiles);
+    return YES;
+  }
+  return NO;
+}
+
 - (BOOL)shouldHighlight {
   BOOL is_menu_open = [menuController_ isMenuOpen];
   return isHighlightEnable_ && (inMouseEventSequence_ || is_menu_open);