[fuchsia] add printing::Image::LoadMetafile() stub

libprinting.so was failing to link in component build on Fuchsia.

Bug: 707031
Change-Id: Ic9957f9184cc07c95ddca551c1abcc023f9f1102
Reviewed-on: https://chromium-review.googlesource.com/802093
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#520877}

printing/BUILD.gn

@@ -242,6 +242,10 @@ component("printing") {
       "pdf_transform.h",
     ]
   }
+
+  if (is_fuchsia) {
+    sources += [ "image_fuchsia.cc" ]
+  }
 }
 
 static_library("test_support") {

printing/image_fuchsia.cc

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "printing/image.h"
+
+namespace printing {
+
+bool Image::LoadMetafile(const Metafile& metafile) {
+  NOTIMPLEMENTED();
+  return false;
+}
+
+}  // namespace printing