Fix the TabScrubber always starting from the first tab in full screen mode.

chrome/browser/ui/views/ash/tab_scrubber.cc

 // Copyright (c) 2013 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/ui/views/ash/tab_scrubber.h"
 
 #include <stdint.h>
 
 #include "ash/shell.h"
 #include "ash/wm/window_util.h"
@@ skipping 216 matching lines @@
 void TabScrubber::BeginScrub(Browser* browser,
                              BrowserView* browser_view,
                              float x_offset) {
   DCHECK(browser);
   DCHECK(browser_view);
 
   scrubbing_ = true;
   browser_ = browser;
   tab_strip_ = browser_view->tabstrip();
 
-  Direction direction = (x_offset < 0) ? LEFT : RIGHT;
-  ScrubDirectionChanged(direction);
-
+  // The browser's top view must be revealed first, before we attempt to get the
+  // start point, otherwise that tab's bounds we get in GetStartPoint() will be
+  // wrong.

[James Cook, 2017/01/27 23:21:27]

nice comment

[afakhry, 2017/01/28 00:48:21]

Thanks!

   ImmersiveModeController* immersive_controller =
       browser_view->immersive_mode_controller();
   if (immersive_controller->IsEnabled()) {
     immersive_reveal_lock_.reset(immersive_controller->GetRevealedLock(
         ImmersiveModeController::ANIMATE_REVEAL_YES));
   }
 
+  Direction direction = (x_offset < 0) ? LEFT : RIGHT;
+  ScrubDirectionChanged(direction);
+
   tab_strip_->AddObserver(this);
 }
 
 void TabScrubber::FinishScrub(bool activate) {
   activate_timer_.Stop();
 
   if (browser_ && browser_->window()) {
     BrowserView* browser_view =
         BrowserView::GetBrowserViewForNativeWindow(
             browser_->window()->GetNativeWindow());
@@ skipping 80 matching lines @@
     tab->hover_controller()->HideImmediately();
   }
 
   if (new_index != browser_->tab_strip_model()->active_index()) {
     highlighted_tab_ = new_index;
     new_tab->hover_controller()->Show(views::GlowHoverController::PRONOUNCED);
   } else {
     highlighted_tab_ = -1;
   }
 }