Split content script injections into multiple tasks

extensions/renderer/extension_frame_helper.cc

Index: extensions/renderer/extension_frame_helper.cc
diff --git a/extensions/renderer/extension_frame_helper.cc b/extensions/renderer/extension_frame_helper.cc
index 28245a67354b36fcf2ea955259a8ef002bc6e8ba..3d1657983d45f546eb7a53c47289735e1bcfc053 100644
--- a/extensions/renderer/extension_frame_helper.cc
+++ b/extensions/renderer/extension_frame_helper.cc
@@ -171,6 +171,12 @@ void ExtensionFrameHelper::RunScriptsAtDocumentEnd() {
   // |this| might be dead by now.
 }
 
+void ExtensionFrameHelper::RunScriptsAtDocumentIdle() {
+  RunCallbacksWhileFrameIsValid(weak_ptr_factory_.GetWeakPtr(),
+                                &document_idle_callbacks_);
+  // |this| might be dead by now.
+}
+
 void ExtensionFrameHelper::ScheduleAtDocumentStart(
     const base::Closure& callback) {
   document_element_created_callbacks_.push_back(callback);
@@ -181,6 +187,11 @@ void ExtensionFrameHelper::ScheduleAtDocumentEnd(
   document_load_finished_callbacks_.push_back(callback);
 }
 
+void ExtensionFrameHelper::ScheduleAtDocumentIdle(
+    const base::Closure& callback) {
+  document_idle_callbacks_.push_back(callback);
+}
+
 void ExtensionFrameHelper::DidMatchCSS(
     const blink::WebVector<blink::WebString>& newly_matching_selectors,
     const blink::WebVector<blink::WebString>& stopped_matching_selectors) {