Show the window controls for 3s on entering full-screen mode.

This addresses some discoverability concerns. LMK if you think it's sufficient.

Review URL: https://codereview.chromium.org/418543002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@285617 0039d316-1c4b-4281-b951-d872f2087c98

remoting/webapp/window_frame.css

@@ -170,8 +170,9 @@ body.fullscreen .window-controls-hover-target {
 }
 
 body.fullscreen .window-controls-hover-target:hover,
+body.fullscreen .window-controls-hover-target.menu-opened,
 body.fullscreen .window-controls-hover-target.opened,
-body.fullscreen .window-controls-hover-target.menu-opened {
+body.fullscreen .window-controls-hover-target.preview {
   top: -4px;
   opacity: 1.0;
   box-shadow: 1px 1px 10px rgba(0, 0, 0, 0.5);

remoting/webapp/window_frame.js

@@ -97,6 +97,8 @@ remoting.WindowFrame = function(titleBar) {
       this.updateMaximizeOrRestoreIconTitle_.bind(this));
   chrome.app.window.current().onFullscreened.addListener(
       this.updateMaximizeOrRestoreIconTitle_.bind(this));
+  chrome.app.window.current().onFullscreened.addListener(
+      this.showWindowControlsPreview_.bind(this));
 };
 
 /**
@@ -225,6 +227,24 @@ remoting.WindowFrame.prototype.onHideOptionsMenu_ = function() {
   this.hoverTarget_.classList.remove('menu-opened');
 };
 
+/**
+ * Show the window controls for a few seconds
+ *
+ * @private
+ */
+remoting.WindowFrame.prototype.showWindowControlsPreview_ = function() {
+  /**
+   * @type {HTMLElement}
+   */
+  var target =  this.hoverTarget_;
+  var kPreviewTimeoutMs = 3000;
+  var hidePreview = function() {
+    target.classList.remove('preview');
+  };
+  target.classList.add('preview');
+  window.setTimeout(hidePreview, kPreviewTimeoutMs);
+};
+
 
 /** @type {remoting.WindowFrame} */
-remoting.windowFrame = null;
\ No newline at end of file
+remoting.windowFrame = null;