Add lock to SkPDFDict

src/pdf/SkPDFStream.cpp

Index: src/pdf/SkPDFStream.cpp
diff --git a/src/pdf/SkPDFStream.cpp b/src/pdf/SkPDFStream.cpp
index e570976403382cac79dfcb327030391fa9a08253..815ef481ee2135abab110171975687f6d8a6d28a 100644
--- a/src/pdf/SkPDFStream.cpp
+++ b/src/pdf/SkPDFStream.cpp
@@ -36,15 +36,9 @@ SkPDFStream::SkPDFStream(const SkPDFStream& pdfStream)
         fState = kCompressed_State;
         removeLength = false;
     }
-    SkPDFDict::Iter dict(pdfStream);
-    SkPDFName* key;
-    SkPDFObject* value;
-    SkPDFName lengthName("Length");
-    for (key = dict.next(&value); key != NULL; key = dict.next(&value)) {
-        if (removeLength && *key == lengthName) {
-            continue;
-        }
-        this->insert(key, value);
+    this->mergeFrom(pdfStream);
+    if (removeLength) {
+        this->remove("Length");
     }
 }