MacViews: Modify condition for setting window alpha to 0 on initial display.

ui/views/cocoa/bridged_native_widget.mm

Index: ui/views/cocoa/bridged_native_widget.mm
diff --git a/ui/views/cocoa/bridged_native_widget.mm b/ui/views/cocoa/bridged_native_widget.mm
index d4e0125716d49df204a2ff73a0446574c4832144..c4d2d5c13841a0137a20d09212144e0559fff5a9 100644
--- a/ui/views/cocoa/bridged_native_widget.mm
+++ b/ui/views/cocoa/bridged_native_widget.mm
@@ -578,7 +578,8 @@ NSComparisonResult SubviewSorter(NSViewComparatorValue lhs,
   // mouse clicks till then.
   // TODO(karandeepb): Investigate whether similar technique is needed for other
   // dialog types.
-  if ([window_ isOpaque] && !native_widget_mac_->GetWidget()->IsModal()) {
+  if (layer() && [window_ isOpaque] &&

[tapted, 2016/09/19 07:35:34]

This reminds me a bit of https://codereview.chromium.org/2061693003/ - still a
WIP - but it would alter the states under which layer() is null. (e.g. we could
DCHECK(layer()) here, and return early before this point in the function if
bridged_view_ is ever null.)

One thing to consider: with Widget::InitParams::TYPE_CONTROL, altering this line
changes behaviour. BNW::Init() calls SetVisibilityState before
NWM::InitNativeWidget calls CreateLayer(). So, what should TYPE_CONTROL do wrt
the "flash"?

I think either
 - all TYPE_CONTROL will be transparent anyway, or
 - TYPE_CONTROL isn't used [yet] on Mac -- it was once used for the app list,
but that's no more.

Might need some investigation.

[karandeepb, 2016/09/20 08:04:51]

NativeWidgetAura initializes the layer before showing the window for
TYPE_CONTROL widgets -
https://cs.chromium.org/chromium/src/ui/views/widget/native_widget_aura.cc?dr....
So we seem to be diverging from its behavior. 
Yeah from what I see on codesearch, most of the TYPE_CONTROL widgets are
transparent. Don't think (Not sure) there are any behind one of the MacViews
flags. An example for MacViewsBrowser is the Find In Page popup. I guess we can
defer taking a look at this, till we get an actual bug.

+      !native_widget_mac_->GetWidget()->IsModal()) {
     initial_visibility_suppressed_ = true;
     [window_ setAlphaValue:0.0];
     [window_ setIgnoresMouseEvents:YES];