Gracefully handle child process death in out-of-process plugin loading.

content/browser/plugin_loader_posix.h

 // Copyright (c) 2011 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 CONTENT_BROWSER_PLUGIN_LOADER_POSIX_H_
 #define CONTENT_BROWSER_PLUGIN_LOADER_POSIX_H_
 
 #include <vector>
 
 #include "base/memory/ref_counted.h"
+#include "base/time.h"
 #include "content/browser/plugin_service.h"
 #include "content/browser/utility_process_host.h"
+#include "ipc/ipc_message.h"
 #include "webkit/plugins/webplugininfo.h"
 
+class FilePath;
+class UtilityProcessHost;
+
 namespace base {
 class MessageLoopProxy;
 }
 
-class PluginLoaderPosix : public UtilityProcessHost::Client {
+// This class is responsible for managing the out-of-process plugin loading on
+// POSIX systems. It primarily lives on the IO thread, but has a brief stay on
+// the FILE thread to iterate over plugin directories when it is first
+// constructed.
+//
+// The following is the algorithm used to load plugins:
+// 1. This asks the PluginList for the list of all potential plugins to attempt
+//    to load. This is referred to as the canonical list.
+// 2. The child process this hosts is forked and the canonical list is sent to
+//    it.
+// 3. The child process iterates over the canonical list, attempting to load
+//    each plugin in the order specified by the list. It sends an IPC message
+//    to the browser after each load, indicating success or failure. The two
+//    processes synchronize the position in the vector that will be used to
+//    attempt to load the next plugin.
+// 4. If the child dies during this process, the host forks another child and
+//    resumes loading at the position past the plugin that it just attempted to
+//    load, bypassing the problematic plugin.
+// 5. This algorithm continues until the canonical list has been walked to the
+//    end, after which the list of loaded plugins is set on the PluginList and
+//    the completion callback is run.
+class PluginLoaderPosix : public UtilityProcessHost::Client,
+                                 IPC::Message::Sender {
  public:
-  // Must be called on the IO thread.
-  static void LoadPlugins(base::MessageLoopProxy* target_loop,
-                          const PluginService::GetPluginsCallback& callback);
+  PluginLoaderPosix();
+
+  // Must be called from the IO thread.
+  void LoadPlugins(scoped_refptr<base::MessageLoopProxy> target_loop,
+                   const PluginService::GetPluginsCallback& callback);
 
   // UtilityProcessHost::Client:
   virtual void OnProcessCrashed(int exit_code) OVERRIDE;
   virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
 
+  // IPC::Message::Sender:
+  virtual bool Send(IPC::Message* msg);
+
  private:
-  PluginLoaderPosix(base::MessageLoopProxy* target_loop,
+  struct PendingCallback {
+    PendingCallback(scoped_refptr<base::MessageLoopProxy> target_loop,
                     const PluginService::GetPluginsCallback& callback);
+    ~PendingCallback();
+
+    scoped_refptr<base::MessageLoopProxy> target_loop;
+    PluginService::GetPluginsCallback callback;
+  };
+
   virtual ~PluginLoaderPosix();
 
-  void OnGotPlugins(const std::vector<webkit::WebPluginInfo>& plugins);
+  // Called on the FILE thread to get the list of plugin paths to probe.
+  void GetPluginsToLoad();
+
+  // Must be called on the IO thread.
+  virtual void LoadPluginsInternal();
+
+  // Message handlers.
+  void OnPluginLoaded(const webkit::WebPluginInfo& plugin);
+  void OnPluginLoadFailed(const FilePath& plugin_path);
+
+  // Checks if the plugin path is an internal plugin, and, if it is, adds it to
+  // |loaded_plugins_|.
+  bool MaybeAddInternalPlugin(const FilePath& plugin_path);
+
+  // Runs all the registered callbacks on each's target loop if the condition
+  // for ending the load process is done (i.e. the |next_load_index_| is outside
+  // the ranage of the |canonical_list_|).
+  void RunPendingCallbacks();
+
+  // The process host for which this is a client.
+  UtilityProcessHost* process_host_;
+
+  // A list of paths to plugins which will be loaded by the utility process, in
+  // the order specified by this vector.
+  std::vector<FilePath> canonical_list_;
+
+  // The index in |canonical_list_| of the plugin that the child process will
+  // attempt to load next.
+  size_t next_load_index_;
+
+  // Internal plugins that have been registered at the time of loading.
+  std::vector<webkit::WebPluginInfo> internal_plugins_;
+
+  // A vector of plugins that have been loaded successfully.
+  std::vector<webkit::WebPluginInfo> loaded_plugins_;
 
   // The callback and message loop on which the callback will be run when the
   // plugin loading process has been completed.
-  scoped_refptr<base::MessageLoopProxy> target_loop_;
-  PluginService::GetPluginsCallback callback_;
+  std::vector<PendingCallback> callbacks_;
 
+  // The time at which plugin loading started.
+  base::TimeTicks load_start_time_;
+
+  friend class MockPluginLoaderPosix;
   DISALLOW_COPY_AND_ASSIGN(PluginLoaderPosix);
 };
 
 #endif  // CONTENT_BROWSER_PLUGIN_LOADER_POSIX_H_