SkPDF: do not assert when openStream return nullptr

src/pdf/SkPDFFont.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkData.h"
 #include "SkGlyphCache.h"
 #include "SkPaint.h"
@@ skipping 350 matching lines @@
     SkAdvancedTypefaceMetrics::FontType type = this->getType();
     SkTypeface* face = this->typeface();
     SkASSERT(face);
 
     auto descriptor = sk_make_sp<SkPDFDict>("FontDescriptor");
     add_common_font_descriptor_entries(descriptor.get(), metrics, 0);
 
     int ttcIndex;
     std::unique_ptr<SkStreamAsset> fontAsset(face->openStream(&ttcIndex));
     size_t fontSize = fontAsset ? fontAsset->getLength() : 0;
-    SkASSERT(fontAsset);
-    SkASSERT(fontSize > 0);
-    if (fontSize > 0) {
+    if (0 == fontSize) {
+        SkDebugf("Error: (SkTypeface)(%p)::openStream() returned "
+                 "empty stream (%p) when identified as kType1CID_Font "
+                 "or kTrueType_Font.\n", face, fontAsset.get());
+    } else {
         switch (type) {
             case SkAdvancedTypefaceMetrics::kTrueType_Font: {
                 #ifdef SK_PDF_USE_SFNTLY
                 if (!SkToBool(metrics.fFlags &
                               SkAdvancedTypefaceMetrics::kNotSubsettable_FontFlag)) {
                     sk_sp<SkPDFStream> subsetStream = get_subset_font_stream(
                             std::move(fontAsset), this->glyphUsage(),
                             metrics.fFontName.c_str(), ttcIndex);
                     if (subsetStream) {
                         descriptor->insertObjRef("FontFile2", std::move(subsetStream));
@@ skipping 338 matching lines @@
 
 bool SkPDFFont::CanEmbedTypeface(SkTypeface* typeface, SkPDFCanon* canon) {
     const SkAdvancedTypefaceMetrics* metrics = SkPDFFont::GetMetrics(typeface, canon);
     return metrics && can_embed(*metrics);
 }
 
 void SkPDFFont::drop() {
     fTypeface = nullptr;
     this->SkPDFDict::drop();
 }