Really fix crash when dragging and dropping in chrome://settings/startup

chrome/browser/custom_home_pages_table_model.cc

 // 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 "chrome/browser/custom_home_pages_table_model.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/i18n/rtl.h"
 #include "base/prefs/pref_service.h"
@@ skipping 78 matching lines @@
 
 /**
  * Move a number of existing entries to a new position, reordering the table.
  *
  * We determine the range of elements affected by the move, save the moved
  * elements, compact the remaining ones, and re-insert moved elements.
  * Expects |index_list| to be ordered ascending.
  */
 void CustomHomePagesTableModel::MoveURLs(int insert_before,
                                          const std::vector<int>& index_list) {
-  // Was causing crashes when just a DCHECK(), see http://crbug.com/136576.
-  if (index_list.empty() || insert_before < 0 || insert_before > RowCount()) {
-    NOTREACHED();
-    return;
-  }
+  DCHECK(!index_list.empty());
+  DCHECK(insert_before >= 0 && insert_before <= RowCount())
+    << "Index out of range: " << insert_before;

[Dan Beam, 2013/03/09 00:22:04]

is this meant to stay here or debugging code?  I'd recommend removing the
message if it's meant to stay.  also, if insert_before == RowCount() what
happens?  I know I wrote this code but maybe I was off-by-one.

[dcheng, 2013/03/09 01:06:22]

I figured it didn't matter since it was only going to be included in debugging
builds, but removed.
We need to support this case; otherwise, we wouldn't be able to drag an item to
the end. So the code Just Works (tm) though I haven't traced through why.

 
   // The range of elements that needs to be reshuffled is [ |first|, |last| ).
   int first = std::min(insert_before, index_list.front());
   int last = std::max(insert_before, index_list.back() + 1);
 
   // Save the dragged elements. Also, adjust insertion point if it is before a
   // dragged element.
   std::vector<Entry> moved_entries;
   for (size_t i = 0; i < index_list.size(); ++i) {
     moved_entries.push_back(entries_[index_list[i]]);
@@ skipping 153 matching lines @@
   return NULL;
 }
 
 string16 CustomHomePagesTableModel::FormattedURL(int row) const {
   std::string languages =
       profile_->GetPrefs()->GetString(prefs::kAcceptLanguages);
   string16 url = net::FormatUrl(entries_[row].url, languages);
   url = base::i18n::GetDisplayStringInLTRDirectionality(url);
   return url;
 }