[turbofan] split compilation stats off from HStatistics and track high water marks

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 92e1d2a03489a4b24ec9b8c96d7725b22eec9e2b..c2bdd6609bf600cf9adab235ce9fbe0aa367f335 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -12594,15 +12594,14 @@ void HStatistics::Initialize(CompilationInfo* info) {
 }
 
 
-void HStatistics::Print(const char* stats_name) {
+void HStatistics::Print() {
   PrintF(
       "\n"
       "----------------------------------------"
       "----------------------------------------\n"
-      "--- %s timing results:\n"
+      "--- Hydrogen timing results:\n"
       "----------------------------------------"
-      "----------------------------------------\n",
-      stats_name);
+      "----------------------------------------\n");
   base::TimeDelta sum;
   for (int i = 0; i < times_.length(); ++i) {
     sum += times_[i];