Converts Widget::SetOpacity from char to float

ui/views/widget/native_widget_mac_unittest.mm

 // Copyright 2014 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.
 
 #import "ui/views/widget/native_widget_mac.h"
 
 #import <Cocoa/Cocoa.h>
 
 #import "base/mac/foundation_util.h"
 #import "base/mac/scoped_nsobject.h"
@@ skipping 1241 matching lines @@
   actual = gfx::ScreenRectToNSRect(widget.GetWorkAreaBoundsInScreen());
   EXPECT_TRUE(NSIsEmptyRect(actual));
 }
 
 // Test that Widget opacity can be changed.
 TEST_F(NativeWidgetMacTest, ChangeOpacity) {
   Widget* widget = CreateTopLevelPlatformWidget();
   NSWindow* ns_window = widget->GetNativeWindow();
 
   CGFloat old_opacity = [ns_window alphaValue];
-  widget->SetOpacity(0xAA);
+  widget->SetOpacity(.7f);
   EXPECT_NE(old_opacity, [ns_window alphaValue]);
-  EXPECT_DOUBLE_EQ(0xAA / 255.0, [ns_window alphaValue]);
+  EXPECT_DOUBLE_EQ(.7, [ns_window alphaValue]);
 
   widget->CloseNow();
 }
 
 // Test that NativeWidgetMac::SchedulePaintInRect correctly passes the dirtyRect
 // parameter to BridgedContentView::drawRect, for a titled window (window with a
 // toolbar).
 TEST_F(NativeWidgetMacTest, SchedulePaintInRect_Titled) {
   Widget* widget = CreateTopLevelPlatformWidget();
 
@@ skipping 310 matching lines @@
   lastDirtyRect_ = dirtyRect;
 }
 
 @end
 
 @implementation FocusableTestNSView
 - (BOOL)acceptsFirstResponder {
   return YES;
 }
 @end