Add testing flag for XPS for deterministic ids.

include/device/xps/SkXPSDevice.h

Index: include/device/xps/SkXPSDevice.h
diff --git a/include/device/xps/SkXPSDevice.h b/include/device/xps/SkXPSDevice.h
index 5170957a596c95491d40b8626b5c840c3bb6fc46..2aa7ba8f0d5bf6a038303e9468bdfadbdddffa9f 100644
--- a/include/device/xps/SkXPSDevice.h
+++ b/include/device/xps/SkXPSDevice.h
@@ -26,6 +26,8 @@
 #include "SkTScopedComPtr.h"
 #include "SkTypeface.h"
 
+//#define SK_XPS_USE_DETERMINISTIC_IDS
+
 /** \class SkXPSDevice
 
     The drawing context for the XPS backend.
@@ -172,6 +174,18 @@ private:
 
     SkTArray<TypefaceUse, true> fTypefaces;
 
+    /** Creates a GUID based id and places it into buffer.
+        buffer should have space for at least GUID_ID_LEN wide characters.
+        The string will always be wchar null terminated.
+        XXXXXXXXsXXXXsXXXXsXXXXsXXXXXXXXXXXX0
+        The string may begin with a digit,
+        and so may not be suitable as a bare resource key.
+     */
+    HRESULT createId(wchar_t* buffer, size_t bufferSize, wchar_t sep = '-');
+#ifdef SK_XPS_USE_DETERMINISTIC_IDS
+    decltype(GUID::Data1) fNextId = 0;

[mtklein, 2014/08/22 18:23:34]

Would prefer DWORD, whatever explicitly.

+#endif
+
     HRESULT initXpsDocumentWriter(IXpsOMImageResource* image);
 
     HRESULT createXpsPage(