Add comments about lazy parsing and lazy compilation.

src/preparser.cc

Index: src/preparser.cc
diff --git a/src/preparser.cc b/src/preparser.cc
index fc4481fd868d24b1a13a627db6d961fbdeae5dea..13bbc4100530b53da25cb9aef37019246c8ee679 100644
--- a/src/preparser.cc
+++ b/src/preparser.cc
@@ -1323,16 +1323,15 @@ PreParser::Expression PreParser::ParseFunctionLiteral(
   }
   Expect(Token::RPAREN, CHECK_OK);
 
-  // Determine if the function will be lazily compiled.
-  // Currently only happens to top-level functions.
-  // Optimistically assume that all top-level functions are lazily compiled.
-  bool is_lazily_compiled = (outer_scope_type == GLOBAL_SCOPE &&
-                             !inside_with && allow_lazy() &&
-                             !parenthesized_function_);
+  // See Parser::ParseFunctionLiteral for more information about lazy parsing
+  // and lazy compilation.
+  bool is_lazily_parsed = (outer_scope_type == GLOBAL_SCOPE &&
+                           !inside_with && allow_lazy() &&
+                           !parenthesized_function_);
   parenthesized_function_ = false;
 
   Expect(Token::LBRACE, CHECK_OK);
-  if (is_lazily_compiled) {
+  if (is_lazily_parsed) {
     ParseLazyFunctionLiteralBody(CHECK_OK);
   } else {
     ParseSourceElements(Token::RBRACE, ok);