MacViews: Don't set window's alpha to 0 if window is already visible.

ui/views/cocoa/bridged_native_widget.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/cocoa/bridged_native_widget.h"
 
 #import <objc/runtime.h>
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 560 matching lines @@
     return;
   }
 
   // Non-modal windows are not animated. Hence opaque non-modal windows can
   // appear with a "flash" if they are made visible before the frame from the
   // compositor arrives. To get around this, set the alpha value of the window
   // to 0, till we receive the correct frame from the compositor. Also, ignore
   // mouse clicks till then.
   // TODO(karandeepb): Investigate whether similar technique is needed for other
   // dialog types.
-  if (layer() && [window_ isOpaque] &&
+  if (layer() && [window_ isOpaque] && !window_visible_ &&
       !native_widget_mac_->GetWidget()->IsModal()) {
     initial_visibility_suppressed_ = true;
     [window_ setAlphaValue:0.0];
     [window_ setIgnoresMouseEvents:YES];
   }
 
   if (new_state == SHOW_AND_ACTIVATE_WINDOW) {
     [window_ makeKeyAndOrderFront:nil];
     [NSApp activateIgnoringOtherApps:YES];
   } else {
@@ skipping 798 matching lines @@
   [bridged_view_ setMouseDownCanMoveWindow:draggable];
   // AppKit will not update its cache of mouseDownCanMoveWindow unless something
   // changes. Previously we tried adding an NSView and removing it, but for some
   // reason it required reposting the mouse-down event, and didn't always work.
   // Calling the below seems to be an effective solution.
   [window_ setMovableByWindowBackground:NO];
   [window_ setMovableByWindowBackground:YES];
 }
 
 }  // namespace views