--- a/dom/ipc/ProcessHangMonitor.cpp
+++ b/dom/ipc/ProcessHangMonitor.cpp
@@ -1209,16 +1209,25 @@ HangMonitoredProcess::UserCanceled() {
 
   if (mActor) {
     uint32_t id = mHangData.get_PluginHangData().pluginId();
     mActor->CleanupPluginHang(id, true);
   }
   return NS_OK;
 }
 
+NS_IMETHODIMP
+HangMonitoredProcess::GetChildID(uint64_t* aChildID) {
+  if (!mContentParent) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+  *aChildID = mContentParent->ChildID();
+  return NS_OK;
+}
+
 static bool InterruptCallback(JSContext* cx) {
   if (HangMonitorChild* child = HangMonitorChild::Get()) {
     return child->InterruptCallback();
   }
 
   return true;
 }
 

--- a/dom/ipc/nsIHangReport.idl
+++ b/dom/ipc/nsIHangReport.idl
@@ -35,16 +35,19 @@ interface nsIHangReport : nsISupports
   // Duration of the hang so far.
   readonly attribute double hangDuration;
   readonly attribute AString addonId;
 
   // For PLUGIN_HANGs, this field contains information about the plugin.
   // Only valid for PLUGIN_HANG reports.
   readonly attribute ACString pluginName;
 
+  // The child id of the process in which the hang happened.
+  readonly attribute unsigned long long childID;
+
   // Called by front end code when user ignores or cancels
   // the notification.
   void userCanceled();
 
   // Terminate the slow script if it is still running.
   // Only valid for SLOW_SCRIPT reports.
   void terminateScript();