Added automatic update for plugins based on watching file changes.

chrome/browser/plugin_service.cc

Index: chrome/browser/plugin_service.cc
diff --git a/chrome/browser/plugin_service.cc b/chrome/browser/plugin_service.cc
index 0c8ee4c579650e0d8e4d7e3f96e5a364f6c8e4d2..b3fe7133bba8b753b6c09d455a5086b1b3d8bd48 100644
--- a/chrome/browser/plugin_service.cc
+++ b/chrome/browser/plugin_service.cc
@@ -8,6 +8,7 @@
 
 #include "base/command_line.h"
 #include "base/path_service.h"
+#include "base/stl_util-inl.h"
 #include "base/string_util.h"
 #include "base/threading/thread.h"
 #include "base/utf_string_conversions.h"
@@ -58,6 +59,28 @@ static void NotifyPluginsOfActivation() {
 }
 #endif
 
+static void PurgePluginListCache(bool reload_pages) {
+  for (RenderProcessHost::iterator it = RenderProcessHost::AllHostsIterator();
+       !it.IsAtEnd(); it.Advance()) {
+    it.GetCurrentValue()->Send(new ViewMsg_PurgePluginListCache(reload_pages));
+  }
+}
+
+// Delegate class for monitoring directories.
+class PluginDirWatcherDelegate : public FilePathWatcher::Delegate {
+  virtual void OnFilePathChanged(const FilePath& path) {
+    VLOG(1) << "Watched path changed: " << path.value();
+
+    // Make the plugin list update itself
+    webkit::npapi::PluginList::Singleton()->RefreshPlugins();

[pastarmovj, 2011/01/12 16:51:09]

Problem here was that PurgePluginCache can be executed between an Async call to
a plugin and before it's been processed. This happens in the
PluginThreadAsyncCall UI test. The problem turned up in mac because MacOS
produces some directory change notifications even when there are none (the
frequency is not so high but it turns out to be a access-time change
notification - so it happens more or less when there is plugin activity and we
might want to disable this for mac altogether). However the problem is not
limited to a specific platform and should be tackled in general.

+  }
+  virtual void OnError() {
+    // TODO(pastarmovj): Add some sensible error handling. Maybe silently
+    // stopping the watcher would be enough. Or possibly restart it.
+    NOTREACHED();
+  }
+};
+
 // static
 bool PluginService::enable_chrome_plugins_ = true;
 
@@ -85,7 +108,8 @@ void PluginService::EnableChromePlugins(bool enable) {
 PluginService::PluginService()
     : main_message_loop_(MessageLoop::current()),
       resource_dispatcher_host_(NULL),
-      ui_locale_(g_browser_process->GetApplicationLocale()) {
+      ui_locale_(g_browser_process->GetApplicationLocale()),
+      file_watcher_delegate_(new PluginDirWatcherDelegate()) {
   RegisterPepperPlugins();
 
   // Have the NPAPI plugin list search for Chrome plugins as well.
@@ -122,6 +146,9 @@ PluginService::PluginService()
 
   chrome::RegisterInternalGPUPlugin();
 
+  // Start watching for changes in the plugin list. This means watching
+  // for changes in the Windows registry keys and on both Windows and POSIX
+  // watch for changes in the paths that are expected to contain plugins.
 #if defined(OS_WIN)
   hkcu_key_.Create(
       HKEY_CURRENT_USER, webkit::npapi::kRegistryMozillaPlugins, KEY_NOTIFY);
@@ -145,6 +172,27 @@ PluginService::PluginService()
         user_data_dir.Append("Plugins"));
   }
 #endif
+  // Get the list of all paths for registering the FilePathWatchers
+  // that will track and if needed reload the list of plugins on runtime.
+  std::vector<FilePath> plugin_dirs;
+  webkit::npapi::PluginList::Singleton()->GetPluginDirectories(
+      &plugin_dirs);
+
+  for (size_t i = 0; i < plugin_dirs.size(); ++i) {
+    FilePathWatcher* watcher = new FilePathWatcher();
+    // FilePathWatcher can not handle non-absolute paths under windows.
+#if defined(OS_WIN)
+    if(!plugin_dirs[i].IsAbsolute())
+      continue;
+#endif
+    VLOG(1) << "Watching for changes in: " << plugin_dirs[i].value();
+    BrowserThread::PostTask(
+        BrowserThread::FILE, FROM_HERE,
+        NewRunnableFunction(
+            &PluginService::RegisterFilePathWatcher,
+            watcher, plugin_dirs[i], file_watcher_delegate_));
+    file_watchers_.push_back(watcher);
+  }
 
   registrar_.Add(this, NotificationType::EXTENSION_LOADED,
                  NotificationService::AllSources());
@@ -304,13 +352,6 @@ bool PluginService::GetFirstAllowedPluginInfo(
 #endif
 }
 
-static void PurgePluginListCache(bool reload_pages) {
-  for (RenderProcessHost::iterator it = RenderProcessHost::AllHostsIterator();
-       !it.IsAtEnd(); it.Advance()) {
-    it.GetCurrentValue()->Send(new ViewMsg_PurgePluginListCache(reload_pages));
-  }
-}
-
 void PluginService::OnWaitableEventSignaled(
     base::WaitableEvent* waitable_event) {
 #if defined(OS_WIN)
@@ -322,6 +363,9 @@ void PluginService::OnWaitableEventSignaled(
 
   webkit::npapi::PluginList::Singleton()->RefreshPlugins();
   PurgePluginListCache(true);

[pastarmovj, 2011/01/12 16:51:09]

I can imagine this will lead to the same problem (only that it doesn't happen
all too often)

+#else
+  // This event should only get signaled on a Windows machine.
+  NOTREACHED();
 #endif  // defined(OS_WIN)
 }
 
@@ -386,7 +430,7 @@ void PluginService::Observe(NotificationType type,
       break;
     }
     default:
-      DCHECK(false);
+      NOTREACHED();
   }
 }
 
@@ -428,3 +472,12 @@ void PluginService::RegisterPepperPlugins() {
     webkit::npapi::PluginList::Singleton()->RegisterInternalPlugin(info);
   }
 }
+
+// static
+void PluginService::RegisterFilePathWatcher(
+    FilePathWatcher *watcher,
+    const FilePath& path,
+    FilePathWatcher::Delegate* delegate) {
+  bool result = watcher->Watch(path, delegate);
+  DCHECK(result);
+}