Make the MediaRouterDialogDelegate set initial dialog size in OSX

chrome/browser/ui/cocoa/constrained_window/constrained_window_web_dialog_sheet.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 "chrome/browser/ui/cocoa/constrained_window/constrained_window_web_dialog_sheet.h"
 
 #include "ui/gfx/geometry/size.h"
 #include "ui/web_dialogs/web_dialog_delegate.h"
 
 @implementation WebDialogConstrainedWindowSheet
 
 - (id)initWithCustomWindow:(NSWindow*)customWindow
          webDialogDelegate:(ui::WebDialogDelegate*)delegate {
   if (self = [super initWithCustomWindow:customWindow]) {
     web_dialog_delegate_ = delegate;
   }
 
   return self;
 }
 
 - (void)updateSheetPosition {
   if (web_dialog_delegate_) {
-    gfx::Size size;
+    // If the dialog has autoresizing enabled and |current_size_| has been set,
+    // GetDialogSize() doesn't modify |size|.
+    gfx::Size size(current_size_.width, current_size_.height);
     web_dialog_delegate_->GetDialogSize(&size);
+    DCHECK(!size.IsEmpty());

[groby-ooo-7-16, 2016/09/14 19:30:02]

I'm assuming this triggers only if updateSheetPosition is called before
current_size_ is set via resizeWithNewSize - we're never resizing back to (0,0),
correct?

In that case, I'd suggest initializing |current_size|_ to
ui::kWindowSizeDeterminedLater.size 
(in -initWithCustomWindow)

I think that would do the trick, without the need of a per-platform ifdef, or
more code here. If there's a different sequence that leads here, could you
describe that sequence?

[takumif, 2016/09/14 21:46:43]

Right, the problem was with updateSheetPosition being called before resizing,
and setting it to ui::kWindowSizeDeterminedLater.size solves the problem.

 
-    // If the dialog has autoresizing enabled, |size| will be empty. Use the
-    // last known dialog size.
-    NSSize content_size = size.IsEmpty() ? current_size_ :
-        NSMakeSize(size.width(), size.height());
+    NSSize content_size = NSMakeSize(size.width(), size.height());
     [customWindow_ setContentSize:content_size];
   }
   [super updateSheetPosition];
 }
 
 - (void)resizeWithNewSize:(NSSize)size {

[groby-ooo-7-16, 2016/09/14 19:30:03]

You probably want a DCHECK(!size.IsEmpty()) here, since empty rects are never a
good plan for windows.

[takumif, 2016/09/14 21:46:43]

Checking that height and width are positive, as NSSize doesn't have an isEmpty
method.

   current_size_ = size;
   [customWindow_ setContentSize:current_size_];
 
   // self's updateSheetPosition() sets |customWindow_|'s contentSize to a
   // fixed dialog size. Here, we want to resize to |size| instead. Use
   // super rather than self to bypass the setContentSize() call for the fixed
   // size.
   [super updateSheetPosition];
 }
 
 @end