fixes #3706: add textColor and textShadow as options to .buttonBackground mixin

less/buttons.less

@@ -15,12 +15,10 @@
   font-size: 13px;
   line-height: 20px;
   *line-height: 20px;
-  color: @grayDark;
   text-align: center;
-  text-shadow: 0 1px 1px rgba(255,255,255,.75);
   vertical-align: middle;
   cursor: pointer;
-  .buttonBackground(@btnBackground, @btnBackgroundHighlight);
+  .buttonBackground(@btnBackground, @btnBackgroundHighlight, @grayDark, 0 1px 1px rgba(255,255,255,.75));
   border: 1px solid @btnBorder;
   *border: 0; // Remove the border to prevent IE7's black border on input:focus
   border-bottom-color: darken(@btnBorder, 10%);
@@ -105,23 +103,6 @@
 // Alternate buttons
 // --------------------------------------------------
 
-// Set text color
-// -------------------------
-.btn-primary,
-.btn-primary:hover,
-.btn-warning,
-.btn-warning:hover,
-.btn-danger,
-.btn-danger:hover,
-.btn-success,
-.btn-success:hover,
-.btn-info,
-.btn-info:hover,
-.btn-inverse,
-.btn-inverse:hover {
-  color: @white;
-  text-shadow: 0 -1px 0 rgba(0,0,0,.25);
-}
 // Provide *some* extra contrast for those who can get it
 .btn-primary.active,
 .btn-warning.active,

less/mixins.less

@@ -389,7 +389,9 @@
 }
 
 // Gradient Bar Colors for buttons and alerts
-.gradientBar(@primaryColor, @secondaryColor) {
+.gradientBar(@primaryColor, @secondaryColor, @textColor: #fff, @textShadow: 0 -1px 0 rgba(0,0,0,.25)) {
+  color: @textColor;
+  text-shadow: @textShadow;
   #gradient > .vertical(@primaryColor, @secondaryColor);
   border-color: @secondaryColor @secondaryColor darken(@secondaryColor, 15%);
   border-color: rgba(0,0,0,.1) rgba(0,0,0,.1) fadein(rgba(0,0,0,.1), 15%);
@@ -481,14 +483,15 @@
 
 // Button backgrounds
 // ------------------
-.buttonBackground(@startColor, @endColor) {
+.buttonBackground(@startColor, @endColor, @textColor: #fff, @textShadow: 0 -1px 0 rgba(0,0,0,.25)) {
   // gradientBar will set the background to a pleasing blend of these, to support IE<=9
-  .gradientBar(@startColor, @endColor);
+  .gradientBar(@startColor, @endColor, @textColor, @textShadow);
   *background-color: @endColor; /* Darken IE7 buttons by default so they stand out more given they won't have borders */
   .reset-filter();
 
   // in these cases the gradient won't cover the background, so we override
   &:hover, &:active, &.active, &.disabled, &[disabled] {
+    color: @textColor;
     background-color: @endColor;
     *background-color: darken(@endColor, 5%);
   }