Fix: Factor iOS native image loading into a utility function.

ios/chrome/browser/ui/tools_menu/tools_menu_view_controller.mm

 // Copyright 2014 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 "ios/chrome/browser/ui/tools_menu/tools_menu_view_controller.h"
 
 #include <stdint.h>
 
 #include "base/ios/ios_util.h"
 #import "base/ios/weak_nsobject.h"
@@ skipping 341 matching lines @@
 }
 
 - (ToolsMenuButton*)newButtonForImageIds:(int[2][3])imageIds
                                commandID:(int)commandID
                     accessibilityLabelID:(int)labelID
                           automationName:(NSString*)name
                            reverseForRTL:(BOOL)reverseForRTL {
   ToolsMenuButton* button = [[ToolsMenuButton alloc] initWithFrame:CGRectZero];
   [button setTranslatesAutoresizingMaskIntoConstraints:NO];
 
-  [button setImage:NativeReversableImage(imageIds[0][0], reverseForRTL)
-          forState:UIControlStateNormal];
+  if (imageIds[0][0]) {
+    [button setImage:NativeReversableImage(imageIds[0][0], reverseForRTL)
+            forState:UIControlStateNormal];
+  }
   [[button imageView] setContentMode:UIViewContentModeCenter];
   [button setBackgroundColor:[self backgroundColor]];
   [button setTag:commandID];
   [button setOpaque:YES];
 
   SetA11yLabelAndUiAutomationName(button, labelID, name);
 
-  UIImage* pressedImage = NativeReversableImage(imageIds[0][1], reverseForRTL);
-  if (pressedImage) {
-    [button setImage:pressedImage forState:UIControlStateHighlighted];
+  if (imageIds[0][1]) {
+    UIImage* pressedImage =
+        NativeReversableImage(imageIds[0][1], reverseForRTL);
+    if (pressedImage) {
+      [button setImage:pressedImage forState:UIControlStateHighlighted];
+    }
   }
 
-  UIImage* disabledImage = NativeReversableImage(imageIds[0][2], reverseForRTL);
-  if (disabledImage) {
-    [button setImage:disabledImage forState:UIControlStateDisabled];
+  if (imageIds[0][2]) {
+    UIImage* disabledImage =
+        NativeReversableImage(imageIds[0][2], reverseForRTL);
+    if (disabledImage) {
+      [button setImage:disabledImage forState:UIControlStateDisabled];
+    }
   }
 
   return button;
 }
 
 - (void)addConstraints {
   UIView* contentView = [self contentView];
 
   for (UIButton* button in [self allButtons]) {
     NSDictionary* view = @{ @"button" : button };
@@ skipping 543 matching lines @@
 
 - (void)unreadCountChanged:(NSInteger)unreadCount {
   [[self readingListCell] updateBadgeCount:unreadCount animated:YES];
 }
 
 - (void)unseenStateChanged:(BOOL)unseenItemsExist {
   [[self readingListCell] updateSeenState:unseenItemsExist animated:YES];
 }
 
 @end