[Mac] Refactor the logic of tab dragging out of TabView and into a new helper.

chrome/browser/ui/cocoa/tabs/tab_controller_unittest.mm

 // Copyright (c) 2011 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 <Cocoa/Cocoa.h>
 
 #import "base/memory/scoped_nsobject.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/ui/cocoa/cocoa_test_helper.h"
 #import "chrome/browser/ui/cocoa/tabs/tab_controller.h"
 #import "chrome/browser/ui/cocoa/tabs/tab_controller_target.h"
+#import "chrome/browser/ui/cocoa/tabs/tab_strip_drag_controller.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #import "testing/gtest_mac.h"
 #include "testing/platform_test.h"
 
 // Implements the target interface for the tab, which gets sent messages when
 // the tab is clicked on by the user and when its close box is clicked.
 @interface TabControllerTestTarget : NSObject<TabControllerTarget> {
  @private
   bool selected_;
   bool closed_;
+  scoped_nsobject<TabStripDragController> dragController_;
 }
 - (bool)selected;
 - (bool)closed;
 @end
 
 @implementation TabControllerTestTarget
+- (id)init {
+  if ((self = [super init])) {
+    dragController_.reset(
+        [[TabStripDragController alloc] initWithTabStripController:nil]);
+  }
+  return self;
+}
 - (bool)selected {
   return selected_;
 }
 - (bool)closed {
   return closed_;
 }
 - (void)selectTab:(id)sender {
   selected_ = true;
 }
 - (void)closeTab:(id)sender {
@@ skipping 22 matching lines @@
   return NO;
 }
 - (ui::SimpleMenuModel*)contextMenuModelForController:(TabController*)controller
     menuDelegate:(ui::SimpleMenuModel::Delegate*)delegate {
   ui::SimpleMenuModel* model = new ui::SimpleMenuModel(delegate);
   model->AddItem(1, ASCIIToUTF16("Hello World"));
   model->AddItem(2, ASCIIToUTF16("Allays"));
   model->AddItem(3, ASCIIToUTF16("Chromium"));
   return model;
 }
+- (id<TabDraggingEventTarget>)dragController {
+  return dragController_.get();
+}
 @end
 
 namespace {
 
 CGFloat LeftMargin(NSRect superFrame, NSRect subFrame) {
   return NSMinX(subFrame) - NSMinX(superFrame);
 }
 
 CGFloat RightMargin(NSRect superFrame, NSRect subFrame) {
   return NSMaxX(superFrame) - NSMaxX(subFrame);
@@ skipping 257 matching lines @@
             NSWidth([[controller titleView] frame]));
   EXPECT_EQ(LeftMargin(originalTabFrame, originalTitleFrame),
             LeftMargin([[controller view] frame],
                        [[controller titleView] frame]));
   EXPECT_EQ(RightMargin(originalTabFrame, originalTitleFrame),
             RightMargin([[controller view] frame],
                         [[controller titleView] frame]));
 }
 
 }  // namespace