[Mac] Reimplement HoverButton and HoverImageButton using NSButton.state.

chrome/browser/ui/cocoa/hover_close_button.mm

Index: chrome/browser/ui/cocoa/hover_close_button.mm
diff --git a/chrome/browser/ui/cocoa/hover_close_button.mm b/chrome/browser/ui/cocoa/hover_close_button.mm
index f01a1720b226400c9ccffd6ac7054dfb37f06129..8c62e55b228c6e3604940d1a4ba24fbc6a7f732e 100644
--- a/chrome/browser/ui/cocoa/hover_close_button.mm
+++ b/chrome/browser/ui/cocoa/hover_close_button.mm
@@ -176,25 +176,24 @@ NSString* const kFadeOutValueKeyPath = @"fadeOutValue";
   return bundle.GetNativeImageNamed(imageID).ToNSImage();
 }
 
-- (void)setHoverState:(HoverState)state {
-  if (state != self.hoverState) {
-    previousState_ = self.hoverState;
-    [super setHoverState:state];
-    // Only animate the HoverStateNone case.
-    if (state == kHoverStateNone) {
-      DCHECK(fadeOutAnimation_ == nil);
-      fadeOutAnimation_ =
-          [[GTMKeyValueAnimation alloc] initWithTarget:self
-                                               keyPath:kFadeOutValueKeyPath];
-      [fadeOutAnimation_ setDuration:kCloseAnimationDuration];
-      [fadeOutAnimation_ setFrameRate:kFramesPerSecond];
-      [fadeOutAnimation_ setDelegate:self];
-      [fadeOutAnimation_ startAnimation];
-    } else {
-      // -stopAnimation will call the animationDidStop: delegate method
-      // which will clean up the animation.
-      [fadeOutAnimation_ stopAnimation];
-    }
+- (void)mouseExited:(NSEvent*)event {
+  previousState_ = self.hoverState;
+  [super mouseExited:event];
+
+  // Only animate the HoverStateNone case.
+  if (self.hoverState == kHoverStateNone) {
+    DCHECK(fadeOutAnimation_ == nil);
+    fadeOutAnimation_ =
+        [[GTMKeyValueAnimation alloc] initWithTarget:self
+                                             keyPath:kFadeOutValueKeyPath];
+    [fadeOutAnimation_ setDuration:kCloseAnimationDuration];
+    [fadeOutAnimation_ setFrameRate:kFramesPerSecond];
+    [fadeOutAnimation_ setDelegate:self];
+    [fadeOutAnimation_ startAnimation];
+  } else {
+    // -stopAnimation will call the animationDidStop: delegate method
+    // which will clean up the animation.
+    [fadeOutAnimation_ stopAnimation];
   }
 }