Make sure there is no crash on parsing empty manifest

extensions/browser/file_highlighter.cc

 // Copyright 2013 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 "extensions/browser/file_highlighter.h"
 
 #include <stack>
 
 #include "base/strings/utf_string_conversions.h"
 #include "base/values.h"
@@ skipping 95 matching lines @@
 
   std::string after_feature = GetAfterFeature();
   if (!after_feature.empty())
     dict->SetString(kAfterHighlightKey, base::UTF8ToUTF16(after_feature));
 }
 
 ManifestHighlighter::ManifestHighlighter(const std::string& manifest,
                                          const std::string& key,
                                          const std::string& specific)
     : FileHighlighter(manifest) {
-  start_ = contents_.find('{') + 1;
+  start_ = contents_.find('{');
+  start_ = start_ == std::string::npos ? contents_.size() : start_ + 1;

[Devlin, 2016/08/17 15:14:03]

nit: since we reassign start_ in all cases, I think it's a little more readable
as
size_t value_begin /* not attached to this name */ = contents_.find('{');
start_ = value_begin == std::string::npos ? contents_.size() : value_begin + 1;

and ditto for end_.

[Rafał Chłodnicki, 2016/08/17 15:54:29]

Let me just keep the current version. Proposed style would make things not fit
one line and thus readability would suffer slightly IMO. :)

   end_ = contents_.rfind('}');
+  end_ = end_ == std::string::npos ? contents_.size() : end_;
   Parse(key, specific);
 }
 
 ManifestHighlighter::~ManifestHighlighter() {
 }
 
 
 void ManifestHighlighter::Parse(const std::string& key,
                                 const std::string& specific) {
   // First, try to find the bounds of the full key.
-  if (FindBounds(key, true) /* enforce at top level */ ) {
+  if (FindBounds(key, true) /* enforce at top level */) {
     // If we succeed, and we have a specific location, find the bounds of the
     // specific.
     if (!specific.empty())
-      FindBounds(specific, false /* don't enforce at top level */ );
+      FindBounds(specific, false /* don't enforce at top level */);
 
     // We may have found trailing whitespace. Don't use base::TrimWhitespace,
     // because we want to keep any whitespace we find - just not highlight it.
     size_t trim = contents_.find_last_not_of(" \t\n\r", end_ - 1);
     if (trim < end_ && trim > start_)
       end_ = trim + 1;
   } else {
     // If we fail, then we set start to end so that the highlighted portion is
     // empty.
     start_ = end_;
@@ skipping 76 matching lines @@
   end_ = contents_.find('\n', start_);
 
   // If we went off the end of the string (i.e., the line number was invalid),
   // then move start and end to the end of the string, so that the highlighted
   // portion is empty.
   start_ = start_ == std::string::npos ? contents_.size() : start_;
   end_ = end_ == std::string::npos ? contents_.size() : end_;
 }
 
 }  // namespace extensions