Fix regression: empty tooltip appears in Linux and Chrome OS

ui/views/corewm/tooltip_controller.cc

 // Copyright (c) 2012 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 "ui/views/corewm/tooltip_controller.h"
 
 #include <stddef.h>
 
 #include <utility>
 #include <vector>
@@ skipping 290 matching lines @@
     tooltip_shown_timer_.Stop();
     tooltip_text_ = tooltip_text;
     base::string16 trimmed_text =
         gfx::TruncateString(tooltip_text_, kMaxTooltipLength, gfx::WORD_BREAK);
     // If the string consists entirely of whitespace, then don't both showing it
     // (an empty tooltip is useless).
     base::TrimWhitespace(trimmed_text, base::TRIM_ALL,
                          &tooltip_text_whitespace_trimmed_);
     if (tooltip_text_whitespace_trimmed_.empty()) {
       tooltip_->Hide();
+      tooltip_defer_timer_.Stop();
     } else if (tooltip_show_delayed_) {
       // Initialize the one-shot timer to show the tooltip in a while.
       // If there is already a request queued then cancel it and post the new
       // request. This ensures that tooltip won't show up too early.
       // The delayed appearance of a tooltip is by default.
       if (tooltip_defer_timer_.IsRunning()) {
         tooltip_defer_timer_.Reset();
       } else {
         tooltip_defer_timer_.Start(FROM_HERE, base::TimeDelta::FromMilliseconds(
                                                   kDelayForTooltipUpdateInMs),
@@ skipping 58 matching lines @@
     return;
   if (tooltip_window_)
     tooltip_window_->RemoveObserver(this);
   tooltip_window_ = target;
   if (tooltip_window_)
     tooltip_window_->AddObserver(this);
 }
 
 }  // namespace corewm
 }  // namespace views