SkPDF/Tests: imporve test coverage.

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"
@@ skipping 25 matching lines @@
     return bitmap;
 }
 
 SkBitmap make_invalid_bitmap(SkColorType colorType) {
     return make_invalid_bitmap(
         SkImageInfo::Make(100, 100, colorType, kPremul_SkAlphaType));
 }
 
 }  // namespace
 
-DEF_TEST(PDFInvalidBitmap, reporter) {
+DEF_TEST(SkPDF_InvalidBitmap, reporter) {
     SkDynamicMemoryWStream stream;
     sk_sp<SkDocument> document(SkDocument::MakePDF(&stream));
+    if (!document) {
+        return;
+    }
     SkCanvas* canvas = document->beginPage(100, 100);
 
     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.
 }