Make sure there is no crash on parsing empty manifest

extensions/browser/file_highlighter_unittest.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 <string>
 
 #include "base/logging.h"
 #include "base/strings/string_util.h"
@@ skipping 75 matching lines @@
 
   const char kFeatureWithComment[] = "\"/*foo*/\"";
   ManifestHighlighter feature_with_comment(kManifest, "test_key", "/*foo*/");
   EXPECT_EQ(kFeatureWithComment, feature_with_comment.GetFeature());
 
   // Check with non-ascii characters.
   const char kInternationalFeature[] = "\"international_key\": \"還是不要\"";
   ManifestHighlighter international_feature(
       kManifest, "international_key", std::string());
   EXPECT_EQ(kInternationalFeature, international_feature.GetFeature());
+
+  // Empty manifest. Check that there is no crash.
+  const char kEmptyManifest[] = "";
+  ManifestHighlighter no_feature(kEmptyManifest, std::string(), std::string());
+  EXPECT_EQ(std::string(), no_feature.GetFeature());
 }
 
 TEST(SouceHighlighterUnitTest, SourceHighlighterUnitTest) {
   const char kBasicSourceFile[] = "line one\nline two\nline three";
 
   SourceHighlighter basic1(kBasicSourceFile, 1u);
   EXPECT_EQ("line one", basic1.GetFeature());
   SourceHighlighter basic2(kBasicSourceFile, 2u);
   EXPECT_EQ("line two", basic2.GetFeature());
   SourceHighlighter basic3(kBasicSourceFile, 3u);
   EXPECT_EQ("line three", basic3.GetFeature());
 
   const char kNoNewlineSourceFile[] = "thisisonelonglinewithnobreaksinit";
 
   SourceHighlighter full_line(kNoNewlineSourceFile, 1u);
   EXPECT_EQ(kNoNewlineSourceFile, full_line.GetFeature());
 
   SourceHighlighter line_zero(kNoNewlineSourceFile, 0u);
   EXPECT_EQ(std::string(), line_zero.GetFeature());
 
   SourceHighlighter out_of_bounds(kNoNewlineSourceFile, 2u);
   EXPECT_EQ(std::string(), out_of_bounds.GetFeature());
 }
 
 }  // namespace extensions