More Windows 64b compilation warning fixes

https://codereview.chromium.org/47513017/



git-svn-id: http://skia.googlecode.com/svn/trunk@12315 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/SkGpuDevice.cpp b/src/gpu/SkGpuDevice.cpp
index 747688e..afdc7e9 100644
--- a/src/gpu/SkGpuDevice.cpp
+++ b/src/gpu/SkGpuDevice.cpp
@@ -571,7 +571,7 @@
 
     fContext->drawVertices(grPaint,
                            gPointMode2PrimtiveType[mode],
-                           count,
+                           SkToS32(count),
                            (GrPoint*)pts,
                            NULL,
                            NULL,