Fix scroll-bar behaviour.

remoting/webapp/client_session.js

Index: remoting/webapp/client_session.js
diff --git a/remoting/webapp/client_session.js b/remoting/webapp/client_session.js
index 51b72a751ffca4542a6f4d722a327f867a55f373..49f20221bf8f4be8506dd3fc5424fe4402a3cf95 100644
--- a/remoting/webapp/client_session.js
+++ b/remoting/webapp/client_session.js
@@ -154,18 +154,38 @@ remoting.ClientSession.prototype.setOnStateChange = function(onStateChange) {
 };
 
 /**
- * Called when the connection has been established to set the initial scroll-
- * bar visibility correctly.
+ * Called when the connection has been established, and subsequently when the
+ * window size or scaling settings change, to set the scroll-bar visibility.
  *
  * TODO(jamiewalch): crbug.com/252796: Remove this once crbug.com/240772 is
  * fixed.
  */
 remoting.ClientSession.prototype.setScrollbarVisibility = function() {
+  // Determine whether or not horizontal or vertical scrollbars are required,
+  // taking into account their width.
+  var kScrollBarWidth = 16;
+  var needsVerticalScroll =
+      !this.shrinkToFit_ && window.innerHeight < this.plugin.desktopHeight;
+  var needsHorizontalScroll =
+      !this.shrinkToFit_ && window.innerWidth < this.plugin.desktopWidth;
+  if (needsHorizontalScroll && !needsVerticalScroll) {
+    needsVerticalScroll =
+        window.innerHeight - kScrollBarWidth < this.plugin.desktopHeight;
+  } else if (!needsHorizontalScroll && needsVerticalScroll) {
+    needsHorizontalScroll =
+        window.innerWidth - kScrollBarWidth < this.plugin.desktopWidth;
+  }
+
   var htmlNode = /** @type {HTMLElement} */ (document.body.parentNode);
-  if (this.shrinkToFit_) {
-    htmlNode.classList.add('no-scroll');
+  if (needsHorizontalScroll) {
+    htmlNode.classList.remove('no-horizontal-scroll');
   } else {
-    htmlNode.classList.remove('no-scroll');
+    htmlNode.classList.add('no-horizontal-scroll');
+  }
+  if (needsVerticalScroll) {
+    htmlNode.classList.remove('no-vertical-scroll');
+  } else {
+    htmlNode.classList.add('no-vertical-scroll');
   }
 };
 
@@ -930,6 +950,8 @@ remoting.ClientSession.prototype.onResize = function() {
   // If bump-scrolling is enabled, adjust the plugin margins to fully utilize
   // the new window area.
   this.scroll_(0, 0);
+
+  this.setScrollbarVisibility();

[Wez, 2013/08/03 00:47:18]

nit: Add a comment e.g. "Show or hide the scrollbars dependent upon the new
size."

[Jamie, 2013/08/03 01:35:55]

This feels like a classic "Add 1 to x" style comment. I don't think it adds
anything to readability.

 };
 
 /**