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..26b20c4c28ce2da4babe31ddf2a471a092618cf2 100644
--- a/remoting/webapp/client_session.js
+++ b/remoting/webapp/client_session.js
@@ -161,11 +161,31 @@ remoting.ClientSession.prototype.setOnStateChange = function(onStateChange) {
  * fixed.
  */
 remoting.ClientSession.prototype.setScrollbarVisibility = function() {
+  // Determine whether or not horizontal or vertical scrollbars are required,
+  // taking into account their width.
+  var kScrollBarWidth = 16;

[Wez, 2013/08/03 00:19:51]

Is this defined in our CSS?

[Jamie, 2013/08/03 00:36:16]

Yes.

+  var needsVerticalScroll =
+      !this.shrinkToFit_ && window.innerHeight < this.plugin.desktopHeight;

[Wez, 2013/08/03 00:19:51]

nit: Might be clearer to just skip this logic entirely in the srhink-to-fit
case.

[Jamie, 2013/08/03 00:36:16]

I think it's clearer this way. The variables are called needs*Scroll, which is
trivially false if shrink-to-fit is enabled.

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

Yes, exactly. So why not:

needsHScroll = false;
needsVScroll = false;
if (!this.shrinkToFit_) {
  <complicated logic goes here!>
}
<mess with styles>

[Jamie, 2013/08/03 01:35:54]

Done.

+  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();
 };
 
 /**