XPS, DM: add SkDocument::CreateXPS

-   SkDocument::CreateXPS() function added, returns NULL on non-Windows OS.

-   DM: (Windows only) an XPSSink is added, fails on non-Windows OS

-   DM: Common code for PDFSink::draw and XPSSink::draw are factored into
    draw_skdocument static function.

-   SkDocument_XPS (Windows only) implementation of SkDocument via
    SkXPSDevice.

-   SkDocument_XPS_None (non-Windows) returns NULL for
    SkDocument::CreateXPS().

-   gyp/xps.gyp refactored.

-   SkXPSDevice::drawTextOnPath removed (see http://crrev.com/925343003 )

-   SkXPSDevice::drawPath supports conics via SkAutoConicToQuads.

Review URL: https://codereview.chromium.org/963953002
diff --git a/dm/DM.cpp b/dm/DM.cpp
index 1c6d322..24808cf 100644
--- a/dm/DM.cpp
+++ b/dm/DM.cpp
@@ -236,6 +236,7 @@
         SINK("skp",  SKPSink);
         SINK("svg",  SVGSink);
         SINK("null", NullSink);
+        SINK("xps",  XPSSink);
     }
 #undef SINK
     return NULL;