Widget opacity goes from 0 to 1, not 0 to 255.

chrome/browser/ui/views/download/download_started_animation_views.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 "chrome/browser/download/download_started_animation.h"
 
 #include "base/macros.h"
 #include "content/public/browser/web_contents.h"
 #include "grit/theme_resources.h"
 #include "ui/base/resource/resource_bundle.h"
@@ skipping 62 matching lines @@
 
   SetImage(&download_image);
 
   popup_ = new views::Widget;
 
   views::Widget::InitParams params(views::Widget::InitParams::TYPE_POPUP);
   params.opacity = views::Widget::InitParams::TRANSLUCENT_WINDOW;
   params.accept_events = false;
   params.parent = web_contents->GetNativeView();
   popup_->Init(params);
-  popup_->SetOpacity(0x00);
+  popup_->SetOpacity(0.f);
   popup_->SetContentsView(this);
   Reposition();
   popup_->Show();
 
   Start();
 }
 
 void DownloadStartedAnimationViews::Reposition() {
   // Align the image with the bottom left of the web contents (so that it
   // points to the newly created download).
@@ skipping 24 matching lines @@
   }
 }
 
 }  // namespace
 
 // static
 void DownloadStartedAnimation::Show(content::WebContents* web_contents) {
   // The animation will delete itself when it's finished.
   new DownloadStartedAnimationViews(web_contents);
 }