[Mac] Use private, undocumented Carbon events to make the presentation mode animation better.

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 8b118397a84f02767090d7c46840e1fd002b70f0..fa2876d34f91d650606c8cdec4af987376411e1e 100644
--- a/chrome/browser/ui/cocoa/presentation_mode_controller.mm
+++ b/chrome/browser/ui/cocoa/presentation_mode_controller.mm
@@ -18,6 +18,7 @@ NSString* const kWillLeaveFullscreenNotification =
     @"WillLeaveFullscreenNotification";
 
 namespace {
+
 // The activation zone for the main menu is 4 pixels high; if we make it any
 // smaller, then the menu can be made to appear without the bar sliding down.
 const CGFloat kDropdownActivationZoneHeight = 4;
@@ -32,7 +33,20 @@ const NSTimeInterval kDropdownHideDelay = 0.2;
 // returns 0 when the menu bar is hidden.)
 const CGFloat kFloatingBarVerticalOffset = 22;
 
-}  // end namespace
+OSStatus MenuBarRevealHandler(EventHandlerCallRef handler,
+                              EventRef event,
+                              void* context) {
+  PresentationModeController* self =
+      static_cast<PresentationModeController*>(context);
+  CGFloat reveal = 0;
+  GetEventParameter(event, FOUR_CHAR_CODE('rvlf'), typeCGFloat, NULL,
+      sizeof(CGFloat), NULL, &reveal);
+  if ([self inPresentationMode])
+    [self changeFloatingBarShownFraction:reveal];
+  return CallNextEventHandler(handler, event);
+}
+
+}  // namespace
 
 
 // Helper class to manage animations for the dropdown bar.  Calls
@@ -169,6 +183,11 @@ const CGFloat kFloatingBarVerticalOffset = 22;
   if ((self = [super init])) {
     browserController_ = controller;
     systemFullscreenMode_ = base::mac::kFullScreenModeNormal;
+
+    EventTypeSpec eventSpec = { kEventClassMenu, 2004 };
+    InstallApplicationEventHandler(NewEventHandlerUPP(&MenuBarRevealHandler),
+                                   1, &eventSpec,
+                                   self, &menuBarTrackingHandler_);
   }
 
   // Let the world know what we're up to.
@@ -180,6 +199,9 @@ const CGFloat kFloatingBarVerticalOffset = 22;
 }
 
 - (void)dealloc {
+  RemoveEventHandler(menuBarTrackingHandler_);
+  menuBarTrackingHandler_ = NULL;
+
   DCHECK(!inPresentationMode_);
   DCHECK(!trackingArea_);
   [super dealloc];
@@ -455,6 +477,7 @@ const CGFloat kFloatingBarVerticalOffset = 22;
   if ([browserController_ floatingBarShownFraction] == fraction)
     return;
 
+/*
   // Create the animation and set it up.
   currentAnimation_.reset(
       [[DropdownAnimation alloc] initWithFraction:fraction
@@ -470,6 +493,7 @@ const CGFloat kFloatingBarVerticalOffset = 22;
   [self removeTrackingAreaIfNecessary];
 
   [currentAnimation_ startAnimation];
+  */
 }
 
 - (void)scheduleShowForMouse {