Move metafile printing code from platform canvas to PaintCanvas

cc/paint/paint_canvas.cc

Index: cc/paint/paint_canvas.cc
diff --git a/cc/paint/paint_canvas.cc b/cc/paint/paint_canvas.cc
index 41ae9c0ed63a9462e62b0a1803b12485cd774c9b..87a0bb5e1115b564cddbcec266912a1db34a8540 100644
--- a/cc/paint/paint_canvas.cc
+++ b/cc/paint/paint_canvas.cc
@@ -4,6 +4,12 @@
 
 #include "cc/paint/paint_canvas.h"
 
+#if defined(OS_MACOSX)
+namespace {
+const char kIsPreviewMetafileKey[] = "CrIsPreviewMetafile";
+}
+#endif
+
 namespace cc {
 
 PaintCanvasPassThrough::PaintCanvasPassThrough(SkCanvas* canvas)
@@ -38,4 +44,19 @@ bool ToPixmap(PaintCanvas* canvas, SkPixmap* output) {
   return true;
 }
 
+#if defined(OS_MACOSX)
+void SetIsPreviewMetafile(PaintCanvas* canvas, bool is_preview) {
+  SkMetaData& meta = canvas->getMetaData();
+  meta.setBool(kIsPreviewMetafileKey, is_preview);
+}
+
+bool IsPreviewMetafile(PaintCanvas* canvas) {
+  bool value;
+  SkMetaData& meta = canvas->getMetaData();
+  if (!meta.findBool(kIsPreviewMetafileKey, &value))
+    value = false;
+  return value;
+}
+#endif
+
 }  // namespace cc