Fix border painting on self-painting layers.

sky/tests/framework/flights-app-expected.txt

Index: sky/tests/framework/flights-app-expected.txt
diff --git a/sky/tests/framework/flights-app-expected.txt b/sky/tests/framework/flights-app-expected.txt
index 66b92ac145c7b8be63f2e6a9bc009725850d59f2..7854353e23387c7cfa1e229f58f112f839aad63a 100644
--- a/sky/tests/framework/flights-app-expected.txt
+++ b/sky/tests/framework/flights-app-expected.txt
@@ -138,7 +138,7 @@ layer at (0,77) size 800x586
               RenderParagraph (anonymous) at (0,0) size 35.59x18
                 RenderText {#text} at (0,0) size 36x17
                   text run at (0,0) width 36: "$367"
-layer at (609,509) size 159x59
+layer at (609,509) size 159x59 clip at (610,510) size 157x57

[ojan, 2015/01/27 06:45:22]

Had to at this rebaseline to the patch. It's from the overflow:hidden added to
the test, not from the C++ change.

   RenderFlexibleBox {app-toast} at (609.31,509) size 158.69x59 [border: (1px solid #AEA477)]
     RenderBlock {div} at (7,13.50) size 32x32
       RenderBlock {div} at (0,0) size 32x32 [border: (2px solid #000000)]