Revert r154797: "Move isValid/isCurrentColor from Color to StyleColor"

Source/core/html/track/InbandTextTrack.cpp

 /*
  * Copyright (C) 2012 Apple Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 138 matching lines @@
     cue->setBaseFontSizeRelativeToVideoHeight(cueData->baseFontSize());
     cue->setFontSizeMultiplier(cueData->relativeFontSize());
     cue->setFontName(cueData->fontName());
 
     if (cueData->position() > 0)
         cue->setPosition(lround(cueData->position()), IGNORE_EXCEPTION);
     if (cueData->line() > 0)
         cue->setLine(lround(cueData->line()), IGNORE_EXCEPTION);
     if (cueData->size() > 0)
         cue->setSize(lround(cueData->size()), IGNORE_EXCEPTION);
-    if (cueData->backgroundColor().alpha())
+    if (cueData->backgroundColor().isValid())
         cue->setBackgroundColor(cueData->backgroundColor().rgb());
-    if (cueData->foregroundColor().alpha())
+    if (cueData->foregroundColor().isValid())
         cue->setForegroundColor(cueData->foregroundColor().rgb());
 
     if (cueData->align() == GenericCueData::Start)
         cue->setAlign("start", IGNORE_EXCEPTION);
     else if (cueData->align() == GenericCueData::Middle)
         cue->setAlign("middle", IGNORE_EXCEPTION);
     else if (cueData->align() == GenericCueData::End)
         cue->setAlign("end", IGNORE_EXCEPTION);
     cue->setSnapToLines(false);
 
@@ skipping 15 matching lines @@
     cue->setId(id);
     cue->setCueSettings(settings);
 
     if (hasCue(cue.get()))
         return;
 
     addCue(cue);
 }
 
 } // namespace WebCore