Fixed bug where an empty version string is considered valid.

base/version.h

Index: base/version.h
diff --git a/base/version.h b/base/version.h
index b2ad7f596aee9b1b2b29dad92d41486d747273b0..6b0680a32d54b0e266379dc1d962e28a9318ce45 100644
--- a/base/version.h
+++ b/base/version.h
@@ -9,6 +9,7 @@
 #include <vector>
 
 #include "base/basictypes.h"
+#include "testing/gtest/include/gtest/gtest_prod.h"
 
 class Version {
  public:
@@ -18,6 +19,11 @@ class Version {
   static Version* GetVersionFromString(const std::wstring& version_str);
   static Version* GetVersionFromString(const std::string& version_str);
 
+  // Exposed only so that a Version can be stored in STL containers;
+  // any call to the methods below on a default-constructed Version
+  // will DCHECK.
+  Version();
+
   ~Version() {}
 
   bool Equals(const Version& other) const;
@@ -31,10 +37,14 @@ class Version {
   const std::vector<uint16>& components() const { return components_; }
 
  private:
-  Version() {}
   bool InitFromString(const std::string& version_str);
 
+  bool is_valid_;
   std::vector<uint16> components_;
+
+  FRIEND_TEST(VersionTest, DefaultConstructor);
+  FRIEND_TEST(VersionTest, GetVersionFromString);
+  FRIEND_TEST(VersionTest, Compare);
 };
 
 #endif  // BASE_VERSION_H_