More win64 warning fixes

src/pdf/SkPDFCatalog.cpp

Index: src/pdf/SkPDFCatalog.cpp
diff --git a/src/pdf/SkPDFCatalog.cpp b/src/pdf/SkPDFCatalog.cpp
index 8690b3eaea7b1ede6c78f104d8c285566020c737..adb466c859e020a62c4932074290edb68604482b 100644
--- a/src/pdf/SkPDFCatalog.cpp
+++ b/src/pdf/SkPDFCatalog.cpp
@@ -197,7 +197,7 @@ off_t SkPDFCatalog::setSubstituteResourcesOffsets(off_t fileOffset,
     SkTSet<SkPDFObject*>* targetSet = getSubstituteList(firstPage);
     off_t offsetSum = fileOffset;
     for (int i = 0; i < targetSet->count(); ++i) {
-        offsetSum += setFileOffset((*targetSet)[i], offsetSum);
+        offsetSum += SkToOffT(setFileOffset((*targetSet)[i], offsetSum));
     }
     return offsetSum - fileOffset;
 }