Keep two empty lines between declarations for cpp files

src/x64/assembler-x64.cc

Index: src/x64/assembler-x64.cc
===================================================================
--- src/x64/assembler-x64.cc	(revision 15486)
+++ src/x64/assembler-x64.cc	(working copy)
@@ -902,11 +902,13 @@
   emit(0xF8);
 }
 
+
 void Assembler::cld() {
   EnsureSpace ensure_space(this);
   emit(0xFC);
 }
 
+
 void Assembler::cdq() {
   EnsureSpace ensure_space(this);
   emit(0x99);
@@ -2522,6 +2524,7 @@
   emit(b2 + i);
 }
 
+
 // SSE 2 operations.
 
 void Assembler::movd(XMMRegister dst, Register src) {
@@ -2582,6 +2585,7 @@
   }
 }
 
+
 void Assembler::movdqa(const Operand& dst, XMMRegister src) {
   EnsureSpace ensure_space(this);
   emit(0x66);
@@ -3035,10 +3039,12 @@
   emit(0xC0 | (dst.low_bits() << 3) | src.low_bits());
 }
 
+
 void Assembler::emit_sse_operand(XMMRegister dst, Register src) {
   emit(0xC0 | (dst.low_bits() << 3) | src.low_bits());
 }
 
+
 void Assembler::emit_sse_operand(Register dst, XMMRegister src) {
   emit(0xC0 | (dst.low_bits() << 3) | src.low_bits());
 }
@@ -3075,6 +3081,7 @@
   reloc_info_writer.Write(&rinfo);
 }
 
+
 void Assembler::RecordJSReturn() {
   positions_recorder()->WriteRecordedPositions();
   EnsureSpace ensure_space(this);