Add the source location of the import string to the LoadStatement AST node, for use in tools.

--
MOS_MIGRATED_REVID=111142252
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/Parser.java b/src/main/java/com/google/devtools/build/lib/syntax/Parser.java
index 023a85b..aa37796 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/Parser.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/Parser.java
@@ -1052,7 +1052,7 @@
       return;
     }
 
-    StringLiteral path = parseStringLiteral();
+    StringLiteral importString = parseStringLiteral();
     expect(TokenKind.COMMA);
 
     Map<Identifier, String> symbols = new HashMap<>();
@@ -1070,13 +1070,13 @@
 
     SkylarkImport imp;
     try {
-      imp = SkylarkImports.create(path.getValue());
-      LoadStatement stmt = new LoadStatement(imp, symbols);
+      imp = SkylarkImports.create(importString.getValue());
+      LoadStatement stmt = new LoadStatement(imp, importString.getLocation(), symbols);
       list.add(setLocation(stmt, start, token.left));
     } catch (SkylarkImportSyntaxException e) {
-      String msg = "Load statement parameter '" + path + "' is invalid. "
+      String msg = "Load statement parameter '" + importString + "' is invalid. "
           + e.getMessage();
-      reportError(path.getLocation(), msg);
+      reportError(importString.getLocation(), msg);
     }
   }