[PDF] Fix image references.

src/pdf/SkPDFImage.cpp

Index: src/pdf/SkPDFImage.cpp
diff --git a/src/pdf/SkPDFImage.cpp b/src/pdf/SkPDFImage.cpp
index 6ede7aaf515d54b5155ade6f8b9ee6033eb01cec..fbd37ebd8eba82a4e76ae77c1db7f4e3a52dee6a 100644
--- a/src/pdf/SkPDFImage.cpp
+++ b/src/pdf/SkPDFImage.cpp
@@ -391,11 +391,17 @@ SkPDFImage::SkPDFImage(SkStream* stream,
                        bool isAlpha,
                        const SkIRect& srcRect,
                        EncodeToDCTStream encoder)
-    : fBitmap(bitmap),
-      fIsAlpha(isAlpha),
+    : fIsAlpha(isAlpha),
       fSrcRect(srcRect),
       fEncoder(encoder) {
 
+    if (bitmap.isImmutable()) {
+        fBitmap = bitmap;
+    } else {
+        bitmap.deepCopyTo(&fBitmap, bitmap.config());
+        fBitmap.setImmutable();
+    }
+
     if (stream != NULL) {
         setData(stream);
         fStreamValid = true;