[PDF] Speculative fix for chrome crash w/ SRC xfer mode.

src/pdf/SkPDFDevice.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 "SkPDFDevice.h"
 
 #include "SkAnnotation.h"
@@ skipping 1930 matching lines @@
 
             dstMaskStorage.reset(createFormXObjectFromDevice());
             dstMask = dstMaskStorage.get();
         }
         drawFormXObjectWithMask(addXObjectResource(dst), dstMask, &clipStack,
                                 clipRegion, SkXfermode::kSrcOver_Mode, true);
     }
 
     SkPaint stockPaint;
 
-    if (xfermode == SkXfermode::kClear_Mode) {
+    if (xfermode == SkXfermode::kSrcATop_Mode) {
+        ScopedContentEntry content(this, &clipStack, clipRegion, identity,
+                                   stockPaint);
+        if (content.entry()) {
+            SkPDFUtils::DrawFormXObject(this->addXObjectResource(dst),
+                                        &content.entry()->fContent);
+        }
+    } else if (xfermode == SkXfermode::kClear_Mode || !srcFormXObject.get()) {
         return;
     } else if (xfermode == SkXfermode::kSrc_Mode ||
             xfermode == SkXfermode::kDstATop_Mode) {
         ScopedContentEntry content(this, &clipStack, clipRegion, identity,
                                    stockPaint);
         if (content.entry()) {
             SkPDFUtils::DrawFormXObject(
                     this->addXObjectResource(srcFormXObject.get()),
                     &content.entry()->fContent);
         }
         if (xfermode == SkXfermode::kSrc_Mode) {
             return;
         }
-    } else if (xfermode == SkXfermode::kSrcATop_Mode) {
-        ScopedContentEntry content(this, &clipStack, clipRegion, identity,
-                                   stockPaint);
-        if (content.entry()) {
-            SkPDFUtils::DrawFormXObject(this->addXObjectResource(dst),
-                                        &content.entry()->fContent);
-        }
     }
 
     SkASSERT(xfermode == SkXfermode::kSrcIn_Mode   ||
              xfermode == SkXfermode::kDstIn_Mode   ||
              xfermode == SkXfermode::kSrcOut_Mode  ||
              xfermode == SkXfermode::kDstOut_Mode  ||
              xfermode == SkXfermode::kSrcATop_Mode ||
              xfermode == SkXfermode::kDstATop_Mode ||
              xfermode == SkXfermode::kModulate_Mode);
 
@@ skipping 322 matching lines @@
 }
 
 bool SkPDFDevice::onReadPixels(const SkBitmap& bitmap, int x, int y,
                                SkCanvas::Config8888) {
     return false;
 }
 
 bool SkPDFDevice::allowImageFilter(SkImageFilter*) {
     return false;
 }