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diff --git a/extensions/renderer/user_script_scheduler.h b/extensions/renderer/user_script_scheduler.h
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+++ b/extensions/renderer/user_script_scheduler.h
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+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef EXTENSIONS_RENDERER_USER_SCRIPT_SCHEDULER_H_
+#define EXTENSIONS_RENDERER_USER_SCRIPT_SCHEDULER_H_
+
+#include <map>
+#include <queue>
+
+#include "base/memory/linked_ptr.h"
+#include "base/memory/weak_ptr.h"
+#include "extensions/common/user_script.h"
+
+class RenderView;
+struct ExtensionMsg_ExecuteCode_Params;
+
+namespace blink {
+class WebFrame;
+}
+
+namespace extensions {
+class Dispatcher;
+
+// Implements support for injecting scripts at different times in the document
+// loading process. The different possible time are described in
+// UserScript::RunLocation.
+//
+// Currently, determining idleness is simple: it is whichever of the following
+// happens first:
+//
+// a) When the initial DOM for a page is complete + kUserScriptIdleTimeout,
+// b) or when the page has completely loaded including all subresources.
+//
+// The intent of this mechanism is to prevent user scripts from slowing down
+// fast pages (run after load), while still allowing them to run relatively
+// timely for pages with lots of slow subresources.
+//
+// NOTE: this class does not inherit from RenderViewObserver on purpose.  The
+// reason is that this object is per frame, and a frame can move across
+// RenderViews thanks to adoptNode.  So we have each RenderView's
+// ExtensionHelper proxy these calls to the renderer process' Dispatcher,
+// which contains the mapping from WebFrame to us.
+class UserScriptScheduler {
+ public:
+  UserScriptScheduler(blink::WebFrame* frame, Dispatcher* dispatcher);
+  ~UserScriptScheduler();
+
+  void ExecuteCode(const ExtensionMsg_ExecuteCode_Params& params);
+  void DidCreateDocumentElement();
+  void DidFinishDocumentLoad();
+  void DidFinishLoad();
+  void DidStartProvisionalLoad();
+
+ private:
+  typedef
+    std::queue<linked_ptr<ExtensionMsg_ExecuteCode_Params> >
+    ExecutionQueue;
+
+  // Run user scripts, except if they've already run for this frame, or the
+  // frame has been destroyed.
+  void MaybeRun();
+
+  // Backend for the IPC Message ExecuteCode in addition to being used
+  // internally.
+  void ExecuteCodeImpl(const ExtensionMsg_ExecuteCode_Params& params);
+
+  // Get all child frames of parent_frame, returned by frames_vector.
+  bool GetAllChildFrames(blink::WebFrame* parent_frame,
+                         std::vector<blink::WebFrame*>* frames_vector) const;
+
+  // Call to signify thet the idle timeout has expired.
+  void IdleTimeout();
+
+  base::WeakPtrFactory<UserScriptScheduler> weak_factory_;
+
+  // The Frame we will run scripts in.
+  blink::WebFrame* frame_;
+
+  // The current location in the document loading process.
+  // Will be UserScript::UNDEFINED if it is before any scripts should be run.
+  UserScript::RunLocation current_location_;
+
+  // Whether we have already run the idle scripts.
+  bool has_run_idle_;
+
+  // This is only used if we're for the main frame.
+  std::map<UserScript::RunLocation, ExecutionQueue> pending_execution_map_;
+
+  Dispatcher* dispatcher_;
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_RENDERER_USER_SCRIPT_SCHEDULER_H_