implemented imageDimsWhenDisabled on CPButton

AppKit/CPButton.j

@@ -554,6 +554,7 @@ CPButtonStateMixed  = CPThemeState("mixed");
         [contentView setTextShadowOffset:[self currentValueForThemeAttribute:@"text-shadow-offset"]];
         [contentView setImagePosition:[self currentValueForThemeAttribute:@"image-position"]];
         [contentView setImageScaling:[self currentValueForThemeAttribute:@"image-scaling"]];
+        [contentView setDimsImage:[self hasThemeState:CPThemeStateDisabled] && _imageDimsWhenDisabled];
     }
 }
 

AppKit/_CPImageAndTextView.j

@@ -68,6 +68,7 @@ var HORIZONTAL_MARGIN   = 3.0,
     
     CPCellImagePosition     _imagePosition;
     CPImageScaling          _imageScaling;
+    BOOL                    _shouldDimImage;
     
     CPImage                 _image;
     CPString                _text;
@@ -216,6 +217,16 @@ var HORIZONTAL_MARGIN   = 3.0,
     return _imageScaling;
 }
 
+- (void)setDimsImage:(BOOL)shouldDimImage
+{
+    var shouldDimImage = !!shouldDimImage;
+    if (_shouldDimImage !== shouldDimImage)
+    {
+        _shouldDimImage = shouldDimImage;
+        [self setNeedsLayout];
+    }
+}
+
 - (void)setTextColor:(CPColor)aTextColor
 {
     if (_textColor === aTextColor)
@@ -577,6 +588,13 @@ var HORIZONTAL_MARGIN   = 3.0,
             imageHeight *= scale;
         }
 
+#if PLATFORM(DOM)
+        if (CPFeatureIsCompatible(CPOpacityRequiresFilterFeature))
+            _DOMElement.style.filter = @"alpha(opacity=" + _shouldDimImage ? 50 : 100 + ")";
+        else
+            _DOMElement.style.opacity = _shouldDimImage ? 0.5 : 1.0;
+#endif
+
 #if PLATFORM(DOM)
         _DOMImageElement.width = imageWidth;
         _DOMImageElement.height = imageHeight;