--- a/dom/base/EventSource.cpp
+++ b/dom/base/EventSource.cpp
@@ -196,21 +196,17 @@ EventSource::Init(nsISupports* aOwner,
   nsCOMPtr<nsIPrincipal> principal = scriptPrincipal->GetPrincipal();
   NS_ENSURE_STATE(principal);
 
   mPrincipal = principal;
   mWithCredentials = aWithCredentials;
 
   // The conditional here is historical and not necessarily sane.
   if (JSContext *cx = nsContentUtils::GetCurrentJSContext()) {
-    const char *filename;
-    if (nsJSUtils::GetCallingLocation(cx, &filename, &mScriptLine)) {
-      mScriptFile.AssignASCII(filename);
-    }
-
+    nsJSUtils::GetCallingLocation(cx, mScriptFile, &mScriptLine);
     mInnerWindowID = nsJSUtils::GetCurrentlyRunningCodeInnerWindowID(cx);
   }
 
   // Get the load group for the page. When requesting we'll add ourselves to it.
   // This way any pending requests will be automatically aborted if the user
   // leaves the page.
   nsresult rv;
   nsIScriptContext* sc = GetContextForEventHandlers(&rv);

--- a/dom/base/nsContentUtils.cpp
+++ b/dom/base/nsContentUtils.cpp
@@ -3359,22 +3359,17 @@ nsContentUtils::ReportToConsoleNonLocali
     rv = CallGetService(NS_CONSOLESERVICE_CONTRACTID, &sConsoleService);
     NS_ENSURE_SUCCESS(rv, rv);
   }
 
   nsAutoCString spec;
   if (!aLineNumber) {
     JSContext *cx = GetCurrentJSContext();
     if (cx) {
-      const char* filename;
-      uint32_t lineno;
-      if (nsJSUtils::GetCallingLocation(cx, &filename, &lineno)) {
-        spec = filename;
-        aLineNumber = lineno;
-      }
+      nsJSUtils::GetCallingLocation(cx, spec, &aLineNumber);
     }
   }
   if (spec.IsEmpty() && aURI)
     aURI->GetSpec(spec);
 
   nsCOMPtr<nsIScriptError> errorObject =
       do_CreateInstance(NS_SCRIPTERROR_CONTRACTID, &rv);
   NS_ENSURE_SUCCESS(rv, rv);

--- a/dom/base/nsJSTimeoutHandler.cpp
+++ b/dom/base/nsJSTimeoutHandler.cpp
@@ -168,21 +168,18 @@ CheckCSPForEval(JSContext* aCx, nsGlobal
 
   if (reportViolation) {
     // TODO : need actual script sample in violation report.
     NS_NAMED_LITERAL_STRING(scriptSample,
                             "call to eval() or related function blocked by CSP");
 
     // Get the calling location.
     uint32_t lineNum = 0;
-    const char *fileName;
     nsAutoString fileNameString;
-    if (nsJSUtils::GetCallingLocation(aCx, &fileName, &lineNum)) {
-      AppendUTF8toUTF16(fileName, fileNameString);
-    } else {
+    if (!nsJSUtils::GetCallingLocation(aCx, fileNameString, &lineNum)) {
       fileNameString.AssignLiteral("unknown");
     }
 
     csp->LogViolationDetails(nsIContentSecurityPolicy::VIOLATION_TYPE_EVAL,
                              fileNameString, scriptSample, lineNum,
                              EmptyString(), EmptyString());
   }
 
@@ -228,20 +225,17 @@ nsJSScriptTimeoutHandler::nsJSScriptTime
   }
 
   *aAllowEval = CheckCSPForEval(aCx, aWindow, aError);
   if (aError.Failed() || !*aAllowEval) {
     return;
   }
 
   // Get the calling location.
-  const char *filename;
-  if (nsJSUtils::GetCallingLocation(aCx, &filename, &mLineNo)) {
-    mFileName.Assign(filename);
-  }
+  nsJSUtils::GetCallingLocation(aCx, mFileName, &mLineNo);
 }
 
 nsJSScriptTimeoutHandler::~nsJSScriptTimeoutHandler()
 {
   ReleaseJSObjects();
 }
 
 void
@@ -348,20 +342,17 @@ nsJSScriptTimeoutHandler::Init(nsGlobalW
     if (error.Failed() || !*aAllowEval) {
       return error.ErrorCode();
     }
 
     MOZ_ASSERT(mExpr.IsEmpty());
     AssignJSFlatString(mExpr, expr);
 
     // Get the calling location.
-    const char *filename;
-    if (nsJSUtils::GetCallingLocation(cx, &filename, &mLineNo)) {
-      mFileName.Assign(filename);
-    }
+    nsJSUtils::GetCallingLocation(cx, mFileName, &mLineNo);
   } else if (funobj) {
     *aAllowEval = true;
 
     mozilla::HoldJSObjects(this);
 
     mFunction = new Function(funobj, GetIncumbentGlobal());
 
     // Create our arg array.  argc is the number of arguments passed

--- a/dom/base/nsJSUtils.cpp
+++ b/dom/base/nsJSUtils.cpp
@@ -29,29 +29,38 @@
 
 #include "mozilla/dom/BindingUtils.h"
 #include "mozilla/dom/Element.h"
 #include "mozilla/dom/ScriptSettings.h"
 
 using namespace mozilla::dom;
 
 bool
-nsJSUtils::GetCallingLocation(JSContext* aContext, const char* *aFilename,
+nsJSUtils::GetCallingLocation(JSContext* aContext, nsACString& aFilename,
                               uint32_t* aLineno)
 {
   JS::AutoFilename filename;
-  unsigned lineno = 0;
-
-  if (!JS::DescribeScriptedCaller(aContext, &filename, &lineno)) {
+  if (!JS::DescribeScriptedCaller(aContext, &filename, aLineno)) {
     return false;
   }
 
-  *aFilename = filename.get();
-  *aLineno = lineno;
+  aFilename.Assign(filename.get());
+  return true;
+}
 
+bool
+nsJSUtils::GetCallingLocation(JSContext* aContext, nsAString& aFilename,
+                              uint32_t* aLineno)
+{
+  JS::AutoFilename filename;
+  if (!JS::DescribeScriptedCaller(aContext, &filename, aLineno)) {
+    return false;
+  }
+
+  aFilename.Assign(NS_ConvertUTF8toUTF16(filename.get()));
   return true;
 }
 
 nsIScriptGlobalObject *
 nsJSUtils::GetStaticScriptGlobal(JSObject* aObj)
 {
   if (!aObj)
     return nullptr;

--- a/dom/base/nsJSUtils.h
+++ b/dom/base/nsJSUtils.h
@@ -27,17 +27,19 @@ namespace dom {
 class AutoJSAPI;
 class Element;
 }
 }
 
 class nsJSUtils
 {
 public:
-  static bool GetCallingLocation(JSContext* aContext, const char* *aFilename,
+  static bool GetCallingLocation(JSContext* aContext, nsACString& aFilename,
+                                 uint32_t* aLineno);
+  static bool GetCallingLocation(JSContext* aContext, nsAString& aFilename,
                                  uint32_t* aLineno);
 
   static nsIScriptGlobalObject *GetStaticScriptGlobal(JSObject* aObj);
 
   static nsIScriptContext *GetStaticScriptContext(JSObject* aObj);
 
   /**
    * Retrieve the inner window ID based on the given JSContext.

--- a/dom/indexedDB/IDBRequest.cpp
+++ b/dom/indexedDB/IDBRequest.cpp
@@ -163,26 +163,17 @@ IDBRequest::SetLoggingSerialNumber(uint6
 
 void
 IDBRequest::CaptureCaller(nsAString& aFilename, uint32_t* aLineNo)
 {
   MOZ_ASSERT(aFilename.IsEmpty());
   MOZ_ASSERT(aLineNo);
 
   ThreadsafeAutoJSContext cx;
-
-  const char* filename = nullptr;
-  uint32_t lineNo = 0;
-  if (!nsJSUtils::GetCallingLocation(cx, &filename, &lineNo)) {
-    *aLineNo = 0;
-    return;
-  }
-
-  aFilename.Assign(NS_ConvertUTF8toUTF16(filename));
-  *aLineNo = lineNo;
+  nsJSUtils::GetCallingLocation(cx, aFilename, aLineNo);
 }
 
 void
 IDBRequest::GetSource(
              Nullable<OwningIDBObjectStoreOrIDBIndexOrIDBCursor>& aSource) const
 {
   AssertIsOnOwningThread();
 

--- a/dom/workers/WorkerPrivate.cpp
+++ b/dom/workers/WorkerPrivate.cpp
@@ -5697,23 +5697,17 @@ WorkerPrivate::SetTimeout(JSContext* aCx
       extraArgVals.AppendElement(aArguments[index]);
     }
     newInfo->mExtraArgVals.SwapElements(extraArgVals);
   }
 
   newInfo->mTargetTime = TimeStamp::Now() + newInfo->mInterval;
 
   if (!newInfo->mTimeoutString.IsEmpty()) {
-    const char* filenameChars;
-    uint32_t lineNumber;
-    if (nsJSUtils::GetCallingLocation(aCx, &filenameChars, &lineNumber)) {
-      newInfo->mFilename = filenameChars;
-      newInfo->mLineNumber = lineNumber;
-    }
-    else {
+    if (!nsJSUtils::GetCallingLocation(aCx, newInfo->mFilename, &newInfo->mLineNumber)) {
       NS_WARNING("Failed to get calling location!");
     }
   }
 
   nsAutoPtr<TimeoutInfo>* insertedInfo =
     mTimeouts.InsertElementSorted(newInfo.forget(), GetAutoPtrComparator(mTimeouts));
 
   // If the timeout we just made is set to fire next then we need to update the