Disable PDF in dm for tonight. It's crashy.

dm/DMPDFTask.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "DMPDFTask.h"
 #include "DMExpectationsTask.h"
 #include "DMPDFRasterizeTask.h"
 #include "DMUtil.h"
 #include "DMWriteTask.h"
 #include "SkCommandLineFlags.h"
 #include "SkDocument.h"
 
-DEFINE_bool(pdf, true, "PDF backend master switch.");
+// The PDF backend is not threadsafe.  If you run dm with --pdf repeatedly, you
+// will quickly find yourself crashed.  (while catchsegv out/Release/dm;; end).
+//
+// TODO(mtklein): re-enable by default, maybe moving to its own single thread.
+DEFINE_bool(pdf, false, "PDF backend master switch.");
 
 namespace DM {
 
 PDFTask::PDFTask(const char* suffix,
                  Reporter* reporter,
                  TaskRunner* taskRunner,
                  const Expectations& expectations,
                  skiagm::GMRegistry::Factory factory,
                  RasterizePdfProc rasterizePdfProc)
     : CpuTask(reporter, taskRunner)
@@ skipping 47 matching lines @@
     if (!FLAGS_pdf) {
         return true;
     }
     if (fGM->getFlags() & skiagm::GM::kSkipPDF_Flag) {
         return true;
     }
     return false;
 }
 
 }  // namespace DM