mac: Add basic layout unit test for fullscreen transition.

chrome/browser/ui/cocoa/browser_window_controller_private.mm

Index: chrome/browser/ui/cocoa/browser_window_controller_private.mm
diff --git a/chrome/browser/ui/cocoa/browser_window_controller_private.mm b/chrome/browser/ui/cocoa/browser_window_controller_private.mm
index 6ffb2ca5ebe248c5932e4db0a79fea4b9b7a256d..f0e0aa3adea7c35a04356cc186dfb6c3b551f731 100644
--- a/chrome/browser/ui/cocoa/browser_window_controller_private.mm
+++ b/chrome/browser/ui/cocoa/browser_window_controller_private.mm
@@ -302,9 +302,6 @@ willPositionSheet:(NSWindow*)sheet
     return 0;
 
   CGFloat totalHeight = 0;
-  if (presentationModeController_)
-    totalHeight = [presentationModeController_ floatingBarVerticalOffset];
-
   if ([self hasTabStrip])
     totalHeight += NSHeight([[self tabStripView] frame]);
 
@@ -730,8 +727,7 @@ willPositionSheet:(NSWindow*)sheet
 - (void)adjustUIForSlidingFullscreenStyle:(fullscreen_mac::SlidingStyle)style {
   if (!presentationModeController_) {
     presentationModeController_.reset(
-        [[PresentationModeController alloc] initWithBrowserController:self
-                                                                style:style]);
+        [self newPresentationModeControllerWithStyle:style]);
     [self configurePresentationModeController];
   } else {
     presentationModeController_.get().slidingStyle = style;
@@ -750,6 +746,12 @@ willPositionSheet:(NSWindow*)sheet
   [self layoutSubviews];
 }
 
+- (PresentationModeController*)newPresentationModeControllerWithStyle:
+    (fullscreen_mac::SlidingStyle)style {
+  return [[PresentationModeController alloc] initWithBrowserController:self
+                                                                 style:style];
+}
+
 - (void)enterImmersiveFullscreen {
   // Set to NO by |-windowDidEnterFullScreen:|.
   enteringImmersiveFullscreen_ = YES;