Fixed crashed when activating the context menu for toolbar buttons using Voiceover

chrome/browser/ui/cocoa/clickhold_button_cell.h

Index: chrome/browser/ui/cocoa/clickhold_button_cell.h
diff --git a/chrome/browser/ui/cocoa/clickhold_button_cell.h b/chrome/browser/ui/cocoa/clickhold_button_cell.h
index bcb759f87e532e631b2c03ac5430014ff65bb5e5..a845b267959f2e584f5d513dd023f0643d8b8293 100644
--- a/chrome/browser/ui/cocoa/clickhold_button_cell.h
+++ b/chrome/browser/ui/cocoa/clickhold_button_cell.h
@@ -19,6 +19,8 @@
   NSTimeInterval clickHoldTimeout_;
   id clickHoldTarget_;                  // Weak.
   SEL clickHoldAction_;
+  id accessibilityShowMenuTarget_;                  // Weak.
+  SEL accessibilityShowMenuAction_;
   BOOL trackOnlyInRect_;
   BOOL activateOnDrag_;
 }
@@ -45,6 +47,13 @@
 @property(assign, nonatomic) id clickHoldTarget;
 @property(assign, nonatomic) SEL clickHoldAction;
 
+// Defines what to do when the Show Menu accessibility action is performed.
+// (clickHoldAction should be independent from accessibilityShowMenuAction
+// since different operations, e.g. releasing vs. not releasing a mouse button,
+// may need to be performed for each occasion.)
+@property(assign, nonatomic) id accessibilityShowMenuTarget;
+@property(assign, nonatomic) SEL accessibilityShowMenuAction;
+
 @end  // @interface ClickHoldButtonCell
 
 #endif  // CHROME_BROWSER_UI_COCOA_CLICKHOLD_BUTTON_CELL_H_