Add ifdef guard around gpu-specific code in native windows window.

src/views/win/SkOSWindow_win.cpp

Index: src/views/win/SkOSWindow_win.cpp
diff --git a/src/views/win/SkOSWindow_win.cpp b/src/views/win/SkOSWindow_win.cpp
index aba5a6f4ae89d6f9ddb3331fcf584e1456ca28d1..4b7abb1e96686cbb510b7282c7b83eccdbb65cc7 100644
--- a/src/views/win/SkOSWindow_win.cpp
+++ b/src/views/win/SkOSWindow_win.cpp
@@ -692,9 +692,11 @@ bool SkOSWindow::makeFullscreen() {
     if (fFullscreen) {
         return true;
     }
+#if SK_SUPPORT_GPU
     if (fHGLRC) {
         this->detachGL();
     }
+#endif // SK_SUPPORT_GPU
     // This is hacked together from various sources on the web. It can certainly be improved and be
     // made more robust.