[Mac] Tracking-area hygiene.

When tracking areas have an owner different from the view they are
added to, they can exist past the owner's death.  These have not been
implicated in any crashes, but it's the best idea I have for the bug.

BUG=38441
TEST=none

Review URL: http://codereview.chromium.org/2823013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@50387 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 9 insertions, 0 deletions

diff --git a/chrome/browser/cocoa/gradient_button_cell.mm b/chrome/browser/cocoa/gradient_button_cell.mm
index 15110e8..523b4d7 100644
--- a/chrome/browser/cocoa/gradient_button_cell.mm
+++ b/chrome/browser/cocoa/gradient_button_cell.mm
@@ -88,6 +88,14 @@ static const NSTimeInterval kAnimationHideDuration = 0.4;
   return self;
 }
 
+- (void)dealloc {
+  if (trackingArea_) {
+    [[self controlView] removeTrackingArea:trackingArea_];
+    trackingArea_.reset();
+  }
+  [super dealloc];
+}
+
 - (NSGradient*)gradientForHoverAlpha:(CGFloat)hoverAlpha
                             isThemed:(BOOL)themed {
   CGFloat startAlpha = 0.6 + 0.3 * hoverAlpha;
@@ -146,6 +154,7 @@ static const NSTimeInterval kAnimationHideDuration = 0.4;
   if (showOnly) {
     if (trackingArea_.get()) {
       [self setShowsBorderOnlyWhileMouseInside:NO];
+      [[self controlView] removeTrackingArea:trackingArea_];
     }
     trackingArea_.reset([[NSTrackingArea alloc]
                           initWithRect:[[self controlView]