Re-implement app overlap detection with new extent syntax.

chrome/common/extensions/extension_extent.h

 // Copyright (c) 2010 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.
 
 #ifndef CHROME_COMMON_EXTENSIONS_EXTENSION_EXTENT_H_
 #define CHROME_COMMON_EXTENSIONS_EXTENSION_EXTENT_H_
 
 #include <string>
 #include <vector>
 
 #include "chrome/common/extensions/url_pattern.h"
 #include "googleurl/src/gurl.h"
 
 // Represents the set of URLs an extension uses for web content.
 class ExtensionExtent {
  public:
   typedef std::vector<URLPattern> PatternList;
 
   bool is_empty() const { return patterns_.empty(); }
 
   const PatternList& patterns() const { return patterns_; }
   void AddPattern(const URLPattern& pattern) { patterns_.push_back(pattern); }
   void ClearPaths() { patterns_.clear(); }
 
+  // Test if the extent contains a URL.
   bool ContainsURL(const GURL& url) const;
 
+  // Returns true if there is a single URL that would be in two extents.
+  bool OverlapsWith(const ExtensionExtent& other) const;
+
  private:
   // The list of URL patterns that comprise the extent.
   PatternList patterns_;
 };
 
 #endif  // CHROME_COMMON_EXTENSIONS_EXTENSION_EXTENT_H_