First cut of mini dart:html.

tool/input_sdk/lib/html/html_common/device.dart

Index: tool/input_sdk/lib/html/html_common/device.dart
diff --git a/tool/input_sdk/lib/html/html_common/device.dart b/tool/input_sdk/lib/html/html_common/device.dart
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+// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+part of html_common;
+
+/**
+ * Utils for device detection.
+ */
+class Device {
+  static bool _isOpera;
+  static bool _isIE;
+  static bool _isFirefox;
+  static bool _isWebKit;
+  static String _cachedCssPrefix;
+  static String _cachedPropertyPrefix;
+
+  /**
+   * Gets the browser's user agent. Using this function allows tests to inject
+   * the user agent.
+ * Returns the user agent.
+   */
+  static String get userAgent => window.navigator.userAgent;
+
+  /**
+   * Determines if the current device is running Opera.
+   */
+  static bool get isOpera {
+    if (_isOpera == null) {
+      _isOpera = userAgent.contains("Opera", 0);
+    }
+    return _isOpera;
+  }
+
+  /**
+   * Determines if the current device is running Internet Explorer.
+   */
+  static bool get isIE {
+    if (_isIE == null) {
+      _isIE = !isOpera && userAgent.contains("Trident/", 0);
+    }
+    return _isIE;
+  }
+
+  /**
+   * Determines if the current device is running Firefox.
+   */
+  static bool get isFirefox {
+    if (_isFirefox == null) {
+      _isFirefox = userAgent.contains("Firefox", 0);
+    }
+    return _isFirefox;
+  }
+
+  /**
+   * Determines if the current device is running WebKit.
+   */
+  static bool get isWebKit {
+    if (_isWebKit == null) {
+      _isWebKit = !isOpera && userAgent.contains("WebKit", 0);
+    }
+    return _isWebKit;
+  }
+
+  /**
+   * Gets the CSS property prefix for the current platform.
+   */
+  static String get cssPrefix {
+    String prefix = _cachedCssPrefix;
+    if (prefix != null) return prefix;
+    if (isFirefox) {
+      prefix = '-moz-';
+    } else if (isIE) {
+      prefix = '-ms-';
+    } else if (isOpera) {
+      prefix = '-o-';
+    } else {
+      prefix = '-webkit-';
+    }
+    return _cachedCssPrefix = prefix;
+  }
+
+  /**
+   * Prefix as used for JS property names.
+   */
+  static String get propertyPrefix {
+    String prefix = _cachedPropertyPrefix;
+    if (prefix != null) return prefix;
+    if (isFirefox) {
+      prefix = 'moz';
+    } else if (isIE) {
+      prefix = 'ms';
+    } else if (isOpera) {
+      prefix = 'o';
+    } else {
+      prefix = 'webkit';
+    }
+    return _cachedPropertyPrefix = prefix;
+  }
+
+  /**
+   * Checks to see if the event class is supported by the current platform.
+   */
+  static bool isEventTypeSupported(String eventType) {
+    // Browsers throw for unsupported event names.
+    try {
+      var e = new Event.eventType(eventType, '');
+      return e is Event;
+    } catch (_) { }
+    return false;
+  }
+}