cocoa browser: add accessible tooltip for security state

chrome/browser/ui/cocoa/location_bar/security_state_bubble_decoration.h

 // 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.
 
 #ifndef CHROME_BROWSER_UI_COCOA_LOCATION_BAR_SECURITY_STATE_BUBBLE_DECORATION_H_
 #define CHROME_BROWSER_UI_COCOA_LOCATION_BAR_SECURITY_STATE_BUBBLE_DECORATION_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/macros.h"
@@ skipping 50 matching lines @@
   void DrawWithBackgroundInFrame(NSRect background_frame,
                                  NSRect frame,
                                  NSView* control_view) override;
   bool IsDraggable() override;
   NSPasteboard* GetDragPasteboard() override;
   NSImage* GetDragImage() override;
   NSRect GetDragImageFrame(NSRect frame) override;
   bool OnMousePressed(NSRect frame, NSPoint location) override;
   bool AcceptsMousePress() override;
   NSPoint GetBubblePointInFrame(NSRect frame) override;
+  NSString* GetToolTip() override;
 
   // BubbleDecoration:
   NSColor* GetBackgroundBorderColor() override;
   ui::NinePartImageIds GetBubbleImageIds() override;
 
   // gfx::AnimationDelegate:
   void AnimationProgressed(const gfx::Animation* animation) override;
 
  protected:
   NSColor* GetDarkModeTextColor() override;
@@ skipping 25 matching lines @@
 
   LocationBarViewMac* owner_;  // weak
 
   // Used to disable find bar animations when testing.
   bool disable_animations_during_testing_;
 
   DISALLOW_COPY_AND_ASSIGN(SecurityStateBubbleDecoration);
 };
 
 #endif  // CHROME_BROWSER_UI_COCOA_LOCATION_BAR_SECURITY_STATE_BUBBLE_DECORATION_H_