Fix long tooltips flashing like crazy under Windows.

chrome/browser/renderer_host/render_widget_host_view_win.cc

 // 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_win.h"
 
 #include "app/gfx/canvas.h"
 #include "app/l10n_util.h"
 #include "app/l10n_util_win.h"
 #include "app/resource_bundle.h"
@@ skipping 608 matching lines @@
   // We've been told to destroy.
   // By clearing close_on_deactivate_, we prevent further deactivations
   // (caused by windows messages resulting from the DestroyWindow) from
   // triggering further destructions.  The deletion of this is handled by
   // OnFinalMessage();
   close_on_deactivate_ = false;
   DestroyWindow();
 }
 
 void RenderWidgetHostViewWin::SetTooltipText(const std::wstring& tooltip_text) {
-  if (tooltip_text != tooltip_text_) {
-    tooltip_text_ = tooltip_text;
+  // Clamp the tooltip length to kMaxTooltipLength so that we don't
+  // accidentally DOS the user with a mega tooltip (since Windows doesn't seem
+  // to do this itself).
+  const std::wstring& new_tooltip_text =
+      l10n_util::TruncateString(tooltip_text, kMaxTooltipLength);
 
-    // Clamp the tooltip length to kMaxTooltipLength so that we don't
-    // accidentally DOS the user with a mega tooltip (since Windows doesn't seem
-    // to do this itself).
-    if (tooltip_text_.length() > kMaxTooltipLength)
-      tooltip_text_ = tooltip_text_.substr(0, kMaxTooltipLength);
+  if (new_tooltip_text != tooltip_text_) {
+    tooltip_text_ = new_tooltip_text;
 
     // Need to check if the tooltip is already showing so that we don't
     // immediately show the tooltip with no delay when we move the mouse from
     // a region with no tooltip to a region with a tooltip.
     if (::IsWindow(tooltip_hwnd_) && tooltip_showing_) {
       ::SendMessage(tooltip_hwnd_, TTM_POP, 0, 0);
       ::SendMessage(tooltip_hwnd_, TTM_POPUP, 0, 0);
     }
   } else {
     // Make sure the tooltip gets closed after TTN_POP gets sent. For some
@@ skipping 677 matching lines @@
     // WM_LBUTTONDOWN.
     SetFocus();
   }
 }
 
 void RenderWidgetHostViewWin::ShutdownHost() {
   shutdown_factory_.RevokeAll();
   render_widget_host_->Shutdown();
   // Do not touch any members at this point, |this| has been deleted.
 }