Convert the async device ID getter to a chrome resource host

chrome/browser/renderer_host/pepper/pepper_flash_device_id_host.h

+// Copyright (c) 2012 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 CHROME_BROWSER_RENDERER_HOST_PEPPER_PEPPER_FLASH_DEVICE_ID_HOST_H_
+#define CHROME_BROWSER_RENDERER_HOST_PEPPER_PEPPER_FLASH_DEVICE_ID_HOST_H_
+
+#include "base/memory/weak_ptr.h"
+#include "content/public/browser/browser_thread.h"
+#include "ppapi/host/resource_host.h"
+#include "ppapi/proxy/resource_message_params.h"
+
+class FilePath;
+
+namespace content {
+class BrowserPpapiHost;
+}
+
+namespace chrome {
+
+class PepperFlashDeviceIDHost : public ppapi::host::ResourceHost {
+ public:
+  PepperFlashDeviceIDHost(content::BrowserPpapiHost* host,
+                          PP_Instance instance,
+                          PP_Resource resource);
+  virtual ~PepperFlashDeviceIDHost();
+
+  // ResourceHost override.
+  virtual int32_t OnResourceMessageReceived(
+      const IPC::Message& msg,
+      ppapi::host::HostMessageContext* context) OVERRIDE;
+
+ private:
+  // Helper class to manage the unfortunate number of thread transitions
+  // required for this operation. We must first get the profile info from the
+  // UI thread, and then actually read the file from the FILE thread before
+  // returning to the IO thread to forward the result to the plugin.
+  class Fetcher
+      : public base::RefCountedThreadSafe<
+            Fetcher,
+            content::BrowserThread::DeleteOnIOThread> {
+   public:
+    explicit Fetcher(const base::WeakPtr<PepperFlashDeviceIDHost>& host);
+    ~Fetcher();
+
+    // Schedules the request operation. The host will be called back with
+    // GotDRMContents. On failure, the contents will be empty.
+    void Start(content::BrowserPpapiHost* browser_host);
+
+   private:
+    // Called on the UI thread to get the file path corresponding to the
+    // given render view. It will schedule the resulting file to be read on the
+    // file thread. On error, it will pass the empty path to the file thread.
+    void GetFilePathOnUIThread(int render_process_id,
+                               int render_view_id);
+
+    // Called on the file thread to read the contents of the file and to
+    // forward it to the IO thread. The path will be empty on error (in
+    // which case it will forward the empty string to the IO thread).
+    void ReadDRMFileOnFileThread(const FilePath& path);
+
+    // Called on the IO thread to call back into the device ID host with the
+    // file contents, or the empty string on failure.
+    void ReplyOnIOThread(const std::string& contents);
+
+    // Access only on IO thread (this class is destroyed on the IO thread
+    // to ensure that this is deleted properly, since weak ptrs aren't
+    // threadsafe).
+    base::WeakPtr<PepperFlashDeviceIDHost> host_;
+
+    DISALLOW_COPY_AND_ASSIGN(Fetcher);
+  };
+  friend class Fetcher;
+
+  // IPC message handler.
+  int32_t OnHostMsgGetDeviceID(const ppapi::host::HostMessageContext* context);
+
+  // Called by the fetcher when the DRM ID was retrieved, or the empty string
+  // on error.
+  void GotDRMContents(const std::string& contents);
+
+  base::WeakPtrFactory<PepperFlashDeviceIDHost> factory_;
+
+  content::BrowserPpapiHost* browser_ppapi_host_;
+
+  // When a request is pending, the fetcher will be non-null, and the reply
+  // params will have the appropriate routing info set for the reply.
+  scoped_refptr<Fetcher> fetcher_;
+  ppapi::proxy::ResourceMessageReplyParams reply_params_;
+
+  DISALLOW_COPY_AND_ASSIGN(PepperFlashDeviceIDHost);
+};
+
+}  // namespace chrome
+
+#endif  // CHROME_BROWSER_RENDERER_HOST_PEPPER_PEPPER_FLASH_DEVICE_ID_HOST_H_