Copied from: https://hg.mozilla.org/releases/mozilla-esr38/rev/750e4cfc90f8
Security advisory: https://www.mozilla.org/en-US/security/advisories/mfsa2016-01/
Mozilla Bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1233152

# HG changeset patch
# User Jan de Mooij <jdemooij@mozilla.com>
# Date 1451478493 -3600
# Node ID 750e4cfc90f80df657e44c9c63b1865023d88682
# Parent  93617c30c0df35f719dead526b78649d564f5ac3
Bug 1233152 - Use PersistentRooted for ParseTask script and sourceObject. r=terrence a=abillings

diff --git a/js/src/vm/HelperThreads.cpp b/js/src/vm/HelperThreads.cpp
--- a/js/src/vm/HelperThreads.cpp
+++ b/js/src/vm/HelperThreads.cpp
@@ -198,17 +198,17 @@ static const JSClass parseTaskGlobalClas
 
 ParseTask::ParseTask(ExclusiveContext* cx, JSObject* exclusiveContextGlobal, JSContext* initCx,
                      const char16_t* chars, size_t length,
                      JS::OffThreadCompileCallback callback, void* callbackData)
   : cx(cx), options(initCx), chars(chars), length(length),
     alloc(JSRuntime::TEMP_LIFO_ALLOC_PRIMARY_CHUNK_SIZE),
     exclusiveContextGlobal(initCx, exclusiveContextGlobal),
     callback(callback), callbackData(callbackData),
-    script(nullptr), errors(cx), overRecursed(false)
+    script(initCx->runtime(), nullptr), errors(cx), overRecursed(false)
 {
 }
 
 bool
 ParseTask::init(JSContext* cx, const ReadOnlyCompileOptions& options)
 {
     if (!this->options.copy(cx, options))
         return false;
diff --git a/js/src/vm/HelperThreads.h b/js/src/vm/HelperThreads.h
--- a/js/src/vm/HelperThreads.h
+++ b/js/src/vm/HelperThreads.h
@@ -472,17 +472,17 @@ struct ParseTask
 
     // Callback invoked off the main thread when the parse finishes.
     JS::OffThreadCompileCallback callback;
     void* callbackData;
 
     // Holds the final script between the invocation of the callback and the
     // point where FinishOffThreadScript is called, which will destroy the
     // ParseTask.
-    JSScript* script;
+    PersistentRootedScript script;
 
     // Any errors or warnings produced during compilation. These are reported
     // when finishing the script.
     Vector<frontend::CompileError*> errors;
     bool overRecursed;
 
     ParseTask(ExclusiveContext* cx, JSObject* exclusiveContextGlobal,
               JSContext* initCx, const char16_t* chars, size_t length,