Fix LabelButtonBorder image blending during state transitions

ui/views/controls/button/label_button_border.cc

Index: ui/views/controls/button/label_button_border.cc
diff --git a/ui/views/controls/button/label_button_border.cc b/ui/views/controls/button/label_button_border.cc
index efb80df3a1b5b672855f1151b26902216cd3ac0d..a06376a0efcf9da32d25aff899f0544ac41667b8 100644
--- a/ui/views/controls/button/label_button_border.cc
+++ b/ui/views/controls/button/label_button_border.cc
@@ -6,6 +6,8 @@
 
 #include "base/logging.h"
 #include "grit/ui_resources.h"
+#include "third_party/skia/include/core/SkPaint.h"
+#include "third_party/skia/include/core/SkXfermode.h"
 #include "ui/base/animation/animation.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/gfx/canvas.h"
@@ -119,17 +121,27 @@ void LabelButtonBorder::Paint(const View& view, gfx::Canvas* canvas) {
   ui::NativeTheme::State state = native_theme_delegate->GetThemeState(&extra);
 
   if (animation && animation->is_animating()) {
-    // Composite the background and foreground painters during state animations.
-    int alpha = animation->CurrentValueBetween(0, 0xff);
+    // Fade from the background to the foreground painter during state
+    // animations. This is done by performing an additive blending of the two
+    // states in an intermediate layer.
+    canvas->sk_canvas()->saveLayer(NULL, NULL);
+    SkPaint paint;
+    paint.setXfermode(SkXfermode::Create(SkXfermode::kPlus_Mode));
+
     state = native_theme_delegate->GetBackgroundThemeState(&extra);
-    canvas->SaveLayerAlpha(static_cast<uint8>(0xff - alpha));
+    int alpha = animation->CurrentValueBetween(0, 0xff);
+    paint.setAlpha(0xff - alpha);
+    canvas->sk_canvas()->saveLayer(NULL, &paint);
     PaintHelper(this, canvas, theme, part, state, rect, extra);
-    canvas->Restore();
+    canvas->sk_canvas()->restore();
 
     state = native_theme_delegate->GetForegroundThemeState(&extra);
-    canvas->SaveLayerAlpha(static_cast<uint8>(alpha));
+    paint.setAlpha(alpha);
+    canvas->sk_canvas()->saveLayer(NULL, &paint);
     PaintHelper(this, canvas, theme, part, state, rect, extra);
-    canvas->Restore();
+    canvas->sk_canvas()->restore();
+
+    canvas->sk_canvas()->restore();
   } else {
     PaintHelper(this, canvas, theme, part, state, rect, extra);
   }