Merge to M54: Temporarily work around crash when adding misspelling annotations to accessible strin…

content/browser/accessibility/browser_accessibility_cocoa.mm

 // Copyright (c) 2012 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.
 
 #include <execinfo.h>
 #include <stddef.h>
 #include <stdint.h>
 
 #import "content/browser/accessibility/browser_accessibility_cocoa.h"
 
@@ skipping 272 matching lines @@
   // Be permissive with the start and end offsets.
   if (start_object == end_object && end_offset < start_offset)
     std::swap(start_offset, end_offset);
 
   int trim_length = 0;
   if ((end_object->IsSimpleTextControl() || end_object->IsTextOnlyObject()) &&
       end_offset < static_cast<int>(end_object->GetText().length())) {
     trim_length = static_cast<int>(end_object->GetText().length()) - end_offset;
   }
   int range_length = [text length] - start_offset - trim_length;
+
+  // http://crbug.com/651145
+  // This shouldn't happen, so this is a temporary workaround to prevent
+  // hard crashes.
+  if (range_length < 0)
+    return nil;
+
   DCHECK_GE(range_length, 0);
   NSRange range = NSMakeRange(start_offset, range_length);
   DCHECK_LE(NSMaxRange(range), [text length]);
 
   NSMutableAttributedString* attributed_text =
       [[[NSMutableAttributedString alloc] initWithString:text] autorelease];
   std::vector<const BrowserAccessibility*> text_only_objects =
       BrowserAccessibilityManager::FindTextOnlyObjectsInRange(*start_object,
                                                               *end_object);
   AddMisspelledTextAttributes(text_only_objects, attributed_text);
@@ skipping 2555 matching lines @@
   if (![self instanceActive])
     return [super hash];
   return browserAccessibility_->GetId();
 }
 
 - (BOOL)accessibilityShouldUseUniqueId {
   return YES;
 }
 
 @end