Bug 1434305 - Part 1: Add LazyScript::{compartment,realm} which returns corresponding JSFunction's {compartment,realm}. r=jimb

This is a preparation for functions added in later parts, to handle LazyScript
samely as JSScript in template function etc.

js/src/vm/JSScript.cpp

@@ -4247,6 +4247,18 @@ LazyScript::initScript(JSScript* script)
     script_.set(script);
 }
 
+JS::Compartment*
+LazyScript::compartment() const
+{
+    return function_->compartment();
+}
+
+Realm*
+LazyScript::realm() const
+{
+    return function_->realm();
+}
+
 void
 LazyScript::setEnclosingLazyScript(LazyScript* enclosingLazyScript)
 {

js/src/vm/JSScript.h

@@ -2346,6 +2346,9 @@ class LazyScript : public gc::TenuredCell
         return function_;
     }
 
+    JS::Compartment* compartment() const;
+    Realm* realm() const;
+
     void initScript(JSScript* script);
 
     JSScript* maybeScript() {