Store parser's current line when script elements are created.

Use the newly stored line as the starting line number when
evaluating JS. This ensures that inline scripts will report
errors with meaningful line numbers.

components/script/dom/element.rs

@@ -145,10 +145,25 @@ impl fmt::Debug for Element {
 
 #[derive(PartialEq, HeapSizeOf)]
 pub enum ElementCreator {
-    ParserCreated,
+    ParserCreated(u64),
     ScriptCreated,
 }
 
+impl ElementCreator {
+    pub fn is_parser_created(&self) -> bool {
+        match *self {
+            ElementCreator::ParserCreated(_) => true,
+            ElementCreator::ScriptCreated => false,
+        }
+    }
+    pub fn return_line_number(&self) -> u64 {
+        match *self {
+            ElementCreator::ParserCreated(l) => l,
+            ElementCreator::ScriptCreated => 1,
+        }
+    }
+}
+
 pub enum AdjacentPosition {
     BeforeBegin,
     AfterEnd,