[wasm][asm.js] Adding custom asm.js lexer.

src/parsing/scanner.h

Index: src/parsing/scanner.h
diff --git a/src/parsing/scanner.h b/src/parsing/scanner.h
index 797fe06e45d1de35f257afbdfbdbac21eb2afb58..f097234f5d0edc0afcecf73f419175cb0e5793a3 100644
--- a/src/parsing/scanner.h
+++ b/src/parsing/scanner.h
@@ -325,18 +325,8 @@ class Scanner {
   Token::Value ScanTemplateStart();
   Token::Value ScanTemplateContinuation();
 
-  Handle<String> SourceUrl(Isolate* isolate) const {
-    Handle<String> tmp;
-    if (source_url_.length() > 0) tmp = source_url_.Internalize(isolate);
-    return tmp;
-  }
-
-  Handle<String> SourceMappingUrl(Isolate* isolate) const {
-    Handle<String> tmp;
-    if (source_mapping_url_.length() > 0)
-      tmp = source_mapping_url_.Internalize(isolate);
-    return tmp;
-  }
+  Handle<String> SourceUrl(Isolate* isolate) const;
+  Handle<String> SourceMappingUrl(Isolate* isolate) const;
 
   bool FoundHtmlComment() const { return found_html_comment_; }