BoxBorderPainter should use computed color alpha

Source/core/style/BorderEdge.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/style/BorderEdge.h"
 
 namespace blink {
 
-BorderEdge::BorderEdge(int edgeWidth, const Color& edgeColor, EBorderStyle edgeStyle, bool edgeIsTransparent, bool edgeIsPresent)
+BorderEdge::BorderEdge(int edgeWidth, const Color& edgeColor, EBorderStyle edgeStyle, bool edgeIsPresent)
     : width(edgeWidth)
     , color(edgeColor)
-    , isTransparent(edgeIsTransparent)
     , isPresent(edgeIsPresent)
     , style(edgeStyle)
 {
     if (style == DOUBLE && edgeWidth < 3)
         style = SOLID;
 }
 
 BorderEdge::BorderEdge()
     : width(0)
-    , isTransparent(false)
     , isPresent(false)
     , style(BHIDDEN)
 {
 }
 
 bool BorderEdge::hasVisibleColorAndStyle() const
 {
-    return style > BHIDDEN && !isTransparent;
+    return style > BHIDDEN && color.alpha() > 0;
 }
 
 bool BorderEdge::shouldRender() const
 {
     return isPresent && width && hasVisibleColorAndStyle();
 }
 
 bool BorderEdge::presentButInvisible() const
 {
     return usedWidth() && !hasVisibleColorAndStyle();
 }
 
 bool BorderEdge::obscuresBackgroundEdge() const
 {
-    if (!isPresent || isTransparent || color.hasAlpha() || style == BHIDDEN)
+    if (!isPresent || color.hasAlpha() || style == BHIDDEN)
         return false;
 
     if (style == DOTTED || style == DASHED)
         return false;
 
     return true;
 }
 
 bool BorderEdge::obscuresBackground() const
 {
-    if (!isPresent || isTransparent || color.hasAlpha() || style == BHIDDEN)
+    if (!isPresent || color.hasAlpha() || style == BHIDDEN)
         return false;
 
     if (style == DOTTED || style == DASHED || style == DOUBLE)
         return false;
 
     return true;
 }
 
 int BorderEdge::usedWidth() const
 {
     return isPresent ? width : 0;
 }
 
 int BorderEdge::getDoubleBorderStripeWidth(DoubleBorderStripe stripe) const
 {
     ASSERT(stripe == DoubleBorderStripeOuter || stripe == DoubleBorderStripeInner);
 
     // We need certain integer rounding results.
     return stripe == DoubleBorderStripeOuter
         ? (usedWidth() + 1) / 3
         : (usedWidth() * 2 + 1) / 3;
 }
 
 bool BorderEdge::sharesColorWith(const BorderEdge& other) const
 {
     return color == other.color;
 }
 
 } // namespace blink