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

src/pdf/SkPDFDevice.cpp

Index: src/pdf/SkPDFDevice.cpp
diff --git a/src/pdf/SkPDFDevice.cpp b/src/pdf/SkPDFDevice.cpp
index ff7dd2cd9252475e46eed12a4c8d623a07f4eb68..0b15d6ab43915c591cbb09a0dfb8419af370ce64 100644
--- a/src/pdf/SkPDFDevice.cpp
+++ b/src/pdf/SkPDFDevice.cpp
@@ -1948,7 +1948,14 @@ void SkPDFDevice::finishContentEntry(const SkXfermode::Mode xfermode,
 
     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) {
@@ -1962,13 +1969,6 @@ void SkPDFDevice::finishContentEntry(const SkXfermode::Mode xfermode,
         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   ||