SkPDF: allow PDF module to be disabled in DM and SampleApp

tests/PDFInvalidBitmapTest.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmap.h"
 #include "SkCanvas.h"
 #include "SkDocument.h"
 #include "SkImageInfo.h"
 #include "SkPixelRef.h"
 #include "SkRefCnt.h"
 #include "SkStream.h"
 
 #include "Test.h"
 
+#if SK_SUPPORT_PDF
+
 namespace {
 
 // SkPixelRef which fails to lock, as a lazy pixel ref might if its pixels
 // cannot be generated.
 class InvalidPixelRef : public SkPixelRef {
 public:
     InvalidPixelRef(const SkImageInfo& info) : SkPixelRef(info) {}
 private:
     bool onNewLockPixels(LockRec*) override { return false; }
     void onUnlockPixels() override {
@@ skipping 23 matching lines @@
     canvas->drawBitmap(SkBitmap(), 0, 0);
     canvas->drawBitmap(make_invalid_bitmap(SkImageInfo()), 0, 0);
     canvas->drawBitmap(make_invalid_bitmap(kN32_SkColorType), 0, 0);
     canvas->drawBitmap(make_invalid_bitmap(kIndex_8_SkColorType), 0, 0);
     canvas->drawBitmap(make_invalid_bitmap(kARGB_4444_SkColorType), 0, 0);
     canvas->drawBitmap(make_invalid_bitmap(kRGB_565_SkColorType), 0, 0);
     canvas->drawBitmap(make_invalid_bitmap(kAlpha_8_SkColorType), 0, 0);
 
     // This test passes if it does not crash.
 }
+#endif  // SK_SUPPORT_PDF