A workaround fix for Issue 3693....

chrome/browser/renderer_host/render_widget_host_view_win.cc

Index: chrome/browser/renderer_host/render_widget_host_view_win.cc
===================================================================
--- chrome/browser/renderer_host/render_widget_host_view_win.cc	(revision 12629)
+++ chrome/browser/renderer_host/render_widget_host_view_win.cc	(working copy)
@@ -810,6 +810,12 @@
           return 1;
       }
     }
+
+    // WebKit does not update its IME status when a user clicks a mouse button
+    // to change the input focus onto a popup menu. As a workaround, we finish
+    // an ongoing composition every time when we click a left button.
+    if (message == WM_LBUTTONDOWN)
+      ime_input_.CleanupComposition(m_hWnd);
   }
 
   ForwardMouseEventToRenderer(message, wparam, lparam);