Bug 910220 part 1. Add friend API for determinining whether we're in a strict-mode script. r=waldo

js/src/jsfriendapi.cpp

@@ -342,6 +342,14 @@ js::IsAtomsCompartment(JSCompartment *comp)
     return comp->runtimeFromAnyThread()->isAtomsCompartment(comp);
 }
 
+JS_FRIEND_API(bool)
+js::IsInNonStrictPropertySet(JSContext *cx)
+{
+    jsbytecode *pc;
+    JSScript *script = cx->currentScript(&pc, JSContext::ALLOW_CROSS_COMPARTMENT);
+    return script && !script->strict && (js_CodeSpec[*pc].format & JOF_SET);
+}
+
 JS_FRIEND_API(bool)
 js::IsFunctionObject(JSObject *obj)
 {

js/src/jsfriendapi.h

@@ -266,6 +266,15 @@ IsAtomsCompartment(JSCompartment *comp);
 extern JS_FRIEND_API(bool)
 ReportIfUndeclaredVarAssignment(JSContext *cx, JS::HandleString propname);
 
+/*
+ * Returns whether we're in a non-strict property set (in that we're in a
+ * non-strict script and the bytecode we're on is a property set).  The return
+ * value does NOT indicate any sort of exception was thrown: it's just a
+ * boolean.
+ */
+extern JS_FRIEND_API(bool)
+IsInNonStrictPropertySet(JSContext *cx);
+
 struct WeakMapTracer;
 
 /*