[Mac] Fix Toolbar glimpse during fullscreen transition

chrome/browser/ui/cocoa/presentation_mode_controller.mm

Index: chrome/browser/ui/cocoa/presentation_mode_controller.mm
diff --git a/chrome/browser/ui/cocoa/presentation_mode_controller.mm b/chrome/browser/ui/cocoa/presentation_mode_controller.mm
index 51504cd893917d73a2c923b4325cf4595ec05366..a3d63f5e2c93608361fc5a90a434ef80d7492d60 100644
--- a/chrome/browser/ui/cocoa/presentation_mode_controller.mm
+++ b/chrome/browser/ui/cocoa/presentation_mode_controller.mm
@@ -52,7 +52,7 @@ OSStatus MenuBarRevealHandler(EventHandlerCallRef handler,
   // As such, we should ignore the kMenuBarRevealEventKind event if it gives
   // us a fraction of 0.0 or 1.0, and rely on kEventMenuBarShown and
   // kEventMenuBarHidden to set these values.
-  if ([self isMainWindow]) {
+  if ([self isMainWindow] && ![self isFullscreenTransitionInProgress]) {
     if (GetEventKind(event) == kMenuBarRevealEventKind) {
       CGFloat revealFraction = 0;
       GetEventParameter(event, FOUR_CHAR_CODE('rvlf'), typeCGFloat, NULL,
@@ -426,6 +426,10 @@ OSStatus MenuBarRevealHandler(EventHandlerCallRef handler,
              : 0;
 }
 
+- (BOOL)isFullscreenTransitionInProgress {
+  return [browserController_ isFullscreenTransitionInProgress];
+}
+
 - (BOOL)isMainWindow {
   return [browserController_ window].isMainWindow;
 }