MacViews: Implement Tooltips

ui/base/cocoa/tool_tip_base_view.h

+// Copyright 2015 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.
+
+#ifndef UI_BASE_COCOA_TOOL_TIP_BASE_VIEW_H_
+#define UI_BASE_COCOA_TOOL_TIP_BASE_VIEW_H_
+
+#import <AppKit/AppKit.h>
+
+#import "ui/base/cocoa/base_view.h"
+
+// An NSiew that allows tooltip text to be set at the current mouse location. It
+// can take effect immediately, but won't appear unless the tooltip delay has
+// elapsed.
+UI_BASE_EXPORT
+@interface ToolTipBaseView : BaseView {
+ @private
+  // These are part of the magic tooltip code from WebKit's WebHTMLView:
+  id trackingRectOwner_;  // (not retained)
+  void* trackingRectUserData_;
+  NSTrackingRectTag lastToolTipTag_;
+  base::scoped_nsobject<NSString> toolTip_;
+}
+
+// Set the current tooltip. It is the responsibility of the caller to set a nil
+// tooltip when the mouse cursor leaves the appropriate region.
+- (void)setToolTipAtMousePoint:(NSString*)string;
+
+@end
+
+#endif  // UI_BASE_COCOA_TOOL_TIP_BASE_VIEW_H_