[MacViews] Fix Drag and Drop bugs

ui/views/cocoa/drag_drop_client_mac_unittest.mm

 // Copyright 2016 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.
 
 #import "ui/views/cocoa/drag_drop_client_mac.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/mac/sdk_forward_declarations.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 43 matching lines @@
 
 - (NSInteger)draggingSequenceNumber {
   return 0;
 }
 
 - (id)draggingSource {
   return nil;
 }
 
 - (NSDragOperation)draggingSourceOperationMask {
-  return NSDragOperationNone;
+  return NSDragOperationEvery;
 }
 
 - (NSWindow*)draggingDestinationWindow {
   return nil;
 }
 
 - (NSArray*)namesOfPromisedFilesDroppedAtDestination:(NSURL*)dropDestination {
   return nil;
 }
 
@@ skipping 164 matching lines @@
 
   // Add valid data to the pasteboard and check to see if the target accepts
   // it.
   [pasteboard setString:@"text" forType:NSPasteboardTypeString];
   EXPECT_EQ(DragUpdate(pasteboard), NSDragOperationCopy);
   EXPECT_EQ(Drop(), NSDragOperationMove);
 }
 
 }  // namespace test
 }  // namespace views