7546: Dumb fix to prevent crash related to accessibility keyboard.

Fixes brave/brave-browser#7546

Related upstream bugs:
https://bugs.chromium.org/p/chromium/issues/detail?id=1029719
https://bugs.chromium.org/p/chromium/issues/detail?id=1133086

It is pretty hard to craft a proper fix so we just add an extra
check and try to return quickly (along with sending a pseudo
crash dump).

chromium_src/content/browser/accessibility/browser_accessibility_cocoa.mm

@@ -0,0 +1,14 @@
+/* Copyright (c) 2020 The Brave Authors. All rights reserved.
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "base/debug/dump_without_crashing.h"
+
+#define BRAVE_FORPARAMETER                \
+  if (startOffset < 0 || endOffset < 0) { \
+    base::debug::DumpWithoutCrashing();   \
+    return nil;                           \
+  }
+
+#include "../../../../../../../content/browser/accessibility/browser_accessibility_cocoa.mm"

patches/content-browser-accessibility-browser_accessibility_cocoa.mm.patch

@@ -0,0 +1,12 @@
+diff --git a/content/browser/accessibility/browser_accessibility_cocoa.mm b/content/browser/accessibility/browser_accessibility_cocoa.mm
+index d792b573258714648c8ce66bedc2fbb4e7417028..76bf56f79848d72067cee0835611962dc791cc55 100644
+--- a/content/browser/accessibility/browser_accessibility_cocoa.mm
++++ b/content/browser/accessibility/browser_accessibility_cocoa.mm
+@@ -3164,6 +3164,7 @@ id content::AXTextMarkerRangeFrom(id anchor_textmarker, id focus_textmarker) {
+     endObject = range.focus()->GetAnchor();
+     startOffset = range.anchor()->text_offset();
+     endOffset = range.focus()->text_offset();
++    BRAVE_FORPARAMETER
+     DCHECK(startObject && endObject);
+     DCHECK_GE(startOffset, 0);
+     DCHECK_GE(endOffset, 0);