Base64 bad menu strings

If a string destined for a menu cannot be turned into a CFString,
base64 it to allow for diagnosis.

Bug: 1140620
Change-Id: I78447813c8cfa5cae92e3e02f693313faf5336ad
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2535553
Commit-Queue: Avi Drissman <avi@chromium.org>
Commit-Queue: Leonard Grey <lgrey@chromium.org>
Reviewed-by: Leonard Grey <lgrey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827001}

content/browser/renderer_host/webmenurunner_mac.mm

@@ -6,6 +6,7 @@
 
 #include <stddef.h>
 
+#include "base/base64.h"
 #include "base/strings/sys_string_conversions.h"
 
 @interface WebMenuRunner (PrivateAPI)
@@ -44,6 +45,16 @@
   }
 
   NSString* title = base::SysUTF8ToNSString(item->label.value_or(""));
+  // https://crbug.com/1140620: SysUTF8ToNSString will return nil if the bits
+  // that it is passed cannot be turned into a CFString. If this nil value is
+  // passed to -[NSMenuItem addItemWithTitle:action:keyEquivalent], Chromium
+  // will crash. Therefore, for debugging, if the result is nil, substitute in
+  // the raw bytes, encoded for safety in base64, to allow for investigation.
+  if (!title) {
+    std::string base64;
+    base::Base64Encode(*item->label, &base64);
+    title = base::SysUTF8ToNSString(base64);
+  }
   NSMenuItem* menuItem = [_menu addItemWithTitle:title
                                           action:@selector(menuItemSelected:)
                                    keyEquivalent:@""];