[Interpreter] Preserve source positions in peephole optimizer.

test/cctest/interpreter/bytecode_expectations/ForIn.golden

 #
 # Autogenerated by generate-bytecode-expectations.
 #
 
 ---
 pool type: mixed
 execute: yes
 wrap: yes
 
 ---
@@ skipping 47 matching lines @@
 handlers: [
 ]
 
 ---
 snippet: "
   var x = 'potatoes';
   for (var p in x) { return p; }
 "
 frame size: 8
 parameter count: 1
-bytecode array length: 45
+bytecode array length: 46
 bytecodes: [
   /*   30 E> */ B(StackCheck),
   /*   42 S> */ B(LdaConstant), U8(0),
   /*   42 E> */ B(Star), R(1),
-  /*   68 S> */ B(JumpIfUndefined), U8(38),
-                B(JumpIfNull), U8(36),
+  /*   68 S> */ B(JumpIfUndefined), U8(39),
+                B(JumpIfNull), U8(37),
                 B(ToObject),
                 B(Star), R(3),
                 B(ForInPrepare), R(4),
                 B(LdaZero),
                 B(Star), R(7),
   /*   63 S> */ B(ForInDone), R(7), R(6),
-                B(JumpIfTrue), U8(23),
+                B(JumpIfTrue), U8(24),
                 B(ForInNext), R(3), R(7), R(4), U8(1),
-                B(JumpIfUndefined), U8(10),
+                B(JumpIfUndefined), U8(11),
                 B(Star), R(0),
   /*   54 E> */ B(StackCheck),
                 B(Ldar), R(0),
                 B(Star), R(2),
+  /*   73 S> */ B(Nop),
   /*   85 S> */ B(Return),
                 B(ForInStep), R(7),
                 B(Star), R(7),
-                B(Jump), U8(-24),
+                B(Jump), U8(-25),
                 B(LdaUndefined),
   /*   85 S> */ B(Return),
 ]
 constant pool: [
   InstanceType::ONE_BYTE_INTERNALIZED_STRING_TYPE,
 ]
 handlers: [
 ]
 
 ---
@@ skipping 148 matching lines @@
                 B(LdaUndefined),
   /*   98 S> */ B(Return),
 ]
 constant pool: [
   InstanceType::FIXED_ARRAY_TYPE,
   InstanceType::FIXED_ARRAY_TYPE,
 ]
 handlers: [
 ]