Keep two empty lines between declarations for cpp files

src/hydrogen-gvn.cc

Index: src/hydrogen-gvn.cc
===================================================================
--- src/hydrogen-gvn.cc	(revision 15486)
+++ src/hydrogen-gvn.cc	(working copy)
@@ -123,6 +123,7 @@
   va_end(arguments);
 }
 
+
 // Wrap TraceGVN in macros to avoid the expense of evaluating its arguments when
 // --trace-gvn is off.
 #define TRACE_GVN_1(msg, a1)                    \
@@ -339,6 +340,7 @@
   return *this;
 }
 
+
 void HSideEffectMap::Kill(GVNFlagSet flags) {
   for (int i = 0; i < kNumberOfTrackedSideEffects; i++) {
     GVNFlag changes_flag = HValue::ChangesFlagFromInt(i);
@@ -748,6 +750,7 @@
   int length_;
 };
 
+
 // This is a recursive traversal of the dominator tree but it has been turned
 // into a loop to avoid stack overflows.
 // The logical "stack frames" of the recursion are kept in a list of