VisualStudio10: Initialize the LongestSource at generate time.

There is no need to initialize it at compute time.

Source/cmGlobalVisualStudio10Generator.cxx

@@ -325,19 +325,9 @@ cmLocalGenerator* cmGlobalVisualStudio10Generator::CreateLocalGenerator(
   return new cmLocalVisualStudio10Generator(this, mf);
 }
 
-//----------------------------------------------------------------------------
-bool cmGlobalVisualStudio10Generator::Compute()
-{
-  if (!cmGlobalVisualStudio8Generator::Compute())
-    {
-    return false;
-    }
-  this->LongestSource = LongestSourcePath();
-  return true;
-}
-
 void cmGlobalVisualStudio10Generator::Generate()
 {
+  this->LongestSource = LongestSourcePath();
   this->cmGlobalVisualStudio8Generator::Generate();
   if(this->LongestSource.Length > 0)
     {

Source/cmGlobalVisualStudio10Generator.h

@@ -45,8 +45,6 @@ public:
     std::vector<std::string> const& makeOptions = std::vector<std::string>()
     );
 
-  virtual bool Compute();
-
   ///! create the correct local generator
   virtual cmLocalGenerator *CreateLocalGenerator(cmMakefile* mf);