Add support for UserIdleTime to Linux.

chrome/browser/sync/engine/idle_query_linux.cc

+// Copyright (c) 2009 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.
+#include "chrome/browser/sync/engine/idle_query_linux.h"
+
+#include <X11/Xlib.h>
+#include <X11/extensions/scrnsaver.h>

[William Hesse, 2010/01/27 16:17:17]

I'm not sure that we have this include file listed as a dependency for Chromium.
 What (Debian or Ubuntu) package is it in, that we should have it? 
x11proto-scrnsaver-dev? Is this listed on
http://code.google.com/p/chromium/wiki/LinuxBuildInstructionsPrerequisites?

+
+namespace browser_sync {
+
+class IdleData {
+ public:
+  IdleData() {
+    int event_base;
+    int error_base;
+    display = XOpenDisplay(NULL);
+    if (XScreenSaverQueryExtension(display, &event_base, &error_base)) {
+      mit_info = XScreenSaverAllocInfo();
+    } else {
+      mit_info = NULL;
+    }
+  }
+
+  ~IdleData() {
+    if (display) {
+      XCloseDisplay(display);
+      display = NULL;
+    }
+    if (mit_info) {
+      XFree(mit_info);
+    }
+  }
+
+  XScreenSaverInfo *mit_info;
+  Display *display;
+};
+
+IdleQueryLinux::IdleQueryLinux() : idle_data_(new IdleData()) {
+}
+
+IdleQueryLinux::~IdleQueryLinux() {
+}
+
+int IdleQueryLinux::IdleTime() {
+  if (!idle_data_->mit_info || !idle_data_->display) {
+    return 0;
+  }
+
+  if (XScreenSaverQueryInfo(idle_data_->display,
+                            RootWindow(idle_data_->display, 0),
+                            idle_data_->mit_info)) {
+    return (idle_data_->mit_info->idle) / 1000;
+  } else {
+    return 0;
+  }
+}
+}  // namespace browser_sync