Lower the number of generations in the script compilation

cache to 5 (down from 8). Generations 5, 6, and 7 are 
rarely hit in real browsing sessions (~2% in the best case)
so it seems better to lower the size to avoid carrying around 
too many compiled scripts in the cache.
Review URL: http://codereview.chromium.org/119301

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2116 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/compilation-cache.cc

@@ -36,7 +36,7 @@ enum {
   // The number of script generations tell how many GCs a script can
   // survive in the compilation cache, before it will be flushed if it
   // hasn't been used.
-  NUMBER_OF_SCRIPT_GENERATIONS = 8,
+  NUMBER_OF_SCRIPT_GENERATIONS = 5,
 
   // The compilation cache consists of tables - one for each entry
   // kind plus extras for the script generations.