Fix integer overflow.

ui/views/widget/widget.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/widget/widget.h"
 
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 682 matching lines @@
 
   if (non_client_view_)
     non_client_view_->Layout();
 }
 
 bool Widget::IsFullscreen() const {
   return native_widget_->IsFullscreen();
 }
 
 void Widget::SetOpacity(float opacity) {
+  DCHECK(opacity >= 0.0f);
+  DCHECK(opacity <= 1.0f);
   native_widget_->SetOpacity(opacity);
 }
 
 void Widget::FlashFrame(bool flash) {
   native_widget_->FlashFrame(flash);
 }
 
 View* Widget::GetRootView() {
   return root_view_.get();
 }
@@ skipping 829 matching lines @@
 
 ////////////////////////////////////////////////////////////////////////////////
 // internal::NativeWidgetPrivate, NativeWidget implementation:
 
 internal::NativeWidgetPrivate* NativeWidgetPrivate::AsNativeWidgetPrivate() {
   return this;
 }
 
 }  // namespace internal
 }  // namespace views