Avoid DCHECK failure for chrome:// URLs in autocomplete suggestions

components/omnibox/browser/autocomplete_result.cc

 // 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.
 
 #include "components/omnibox/browser/autocomplete_result.h"
 
 #include <algorithm>
 #include <iterator>
 
 #include "base/command_line.h"
@@ skipping 148 matching lines @@
   if (default_match_ != matches_.end()) {
     const base::string16 debug_info =
         base::ASCIIToUTF16("fill_into_edit=") +
         default_match_->fill_into_edit +
         base::ASCIIToUTF16(", provider=") +
         ((default_match_->provider != NULL)
             ? base::ASCIIToUTF16(default_match_->provider->GetName())
             : base::string16()) +
         base::ASCIIToUTF16(", input=") +
         input.text();
-    DCHECK(default_match_->allowed_to_be_default_match) << debug_info;
-    // If the default match is valid (i.e., not a prompt/placeholder), make
-    // sure the type of destination is what the user would expect given the
-    // input.
-    if (default_match_->destination_url.is_valid()) {
+
+    // We should only get here with an empty omnibox for automatic suggestions
+    // on focus on the NTP; in these cases hitting enter should do nothing, so
+    // there should be no default match.  Otherwise, we're doing automatic
+    // suggestions for the currently visible URL (and hitting enter should
+    // reload it), or the user is typing; in either of these cases, there should
+    // be a default match.
+    DCHECK_NE(input.text().empty(), default_match_->allowed_to_be_default_match)
+        << debug_info;
+
+    // For navigable default matches, make sure the destination type is what the
+    // user would expect given the input.
+    if (default_match_->allowed_to_be_default_match &&
+        default_match_->destination_url.is_valid()) {
       if (AutocompleteMatch::IsSearchType(default_match_->type)) {
         // We shouldn't get query matches for URL inputs.
         DCHECK_NE(metrics::OmniboxInputType::URL, input.type()) << debug_info;
       } else {
         // If the user explicitly typed a scheme, the default match should
         // have the same scheme.
         if ((input.type() == metrics::OmniboxInputType::URL) &&
             input.parts().scheme.is_nonempty()) {
           const std::string& in_scheme = base::UTF16ToUTF8(input.scheme());
           const std::string& dest_scheme =
@@ skipping 195 matching lines @@
        i != old_matches.rend() && delta > 0; ++i) {
     if (!HasMatchByDestination(*i, new_matches)) {
       AutocompleteMatch match = *i;
       match.relevance = std::min(max_relevance, match.relevance);
       match.from_previous = true;
       matches_.push_back(match);
       delta--;
     }
   }
 }