Only show tooltip when window is key....

chrome/browser/renderer_host/render_widget_host_view_mac.mm

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/renderer_host/render_widget_host_view_mac.h"
 
 #include "base/histogram.h"
 #include "base/sys_string_conversions.h"
 #include "chrome/browser/browser_trial.h"
 #include "chrome/browser/renderer_host/backing_store.h"
@@ skipping 249 matching lines @@
 // contained within this view (and are unknown to the NSView system), we
 // are forced to implement our own tooltips with child windows.
 // TODO(pinkerton): Do we want these tooltips to time out after a certain time?
 // Gecko does this automatically in the back-end, hence the ToolTip class not
 // needing that functionality. We can either modify ToolTip or add this
 // functionality here with a timer.
 // TODO(pinkerton): This code really needs to live at a higher level because
 // right now it allows multiple views in multiple tabs to each be displaying
 // a tooltip simultaneously (http://crbug.com/14178).
 void RenderWidgetHostViewMac::SetTooltipText(const std::wstring& tooltip_text) {
-  if (tooltip_text != tooltip_text_ && [[cocoa_view_ window] isMainWindow]) {
+  if (tooltip_text != tooltip_text_ && [[cocoa_view_ window] isKeyWindow]) {
     tooltip_text_ = tooltip_text;
 
     // Clamp the tooltip length to kMaxTooltipLength. It's a DOS issue on
     // Windows; we're just trying to be polite. Don't persist the trimmed
     // string, as then the comparison above will always fail and we'll try to
     // set it again every single time the mouse moves.
     std::wstring display_text = tooltip_text_;
     if (tooltip_text_.length() > kMaxTooltipLength)
       display_text = tooltip_text_.substr(0, kMaxTooltipLength);
 
@@ skipping 222 matching lines @@
 
   if (closeOnDeactivate_)
     renderWidgetHostView_->KillSelf();
 
   renderWidgetHostView_->render_widget_host_->Blur();
 
   return YES;
 }
 
 @end