fix (some) 64bit warnings -- size_t -> int

src/core/SkFontDescriptor.cpp

Index: src/core/SkFontDescriptor.cpp
diff --git a/src/core/SkFontDescriptor.cpp b/src/core/SkFontDescriptor.cpp
index 7679d92a146a8ccc5ac2badb99b29440e5cea499..5088ed7687bcec8dae2954ca2c5d3cf4aaa5b43b 100644
--- a/src/core/SkFontDescriptor.cpp
+++ b/src/core/SkFontDescriptor.cpp
@@ -25,7 +25,7 @@ SkFontDescriptor::SkFontDescriptor(SkTypeface::Style style) {
 }
 
 static void read_string(SkStream* stream, SkString* string) {
-    const uint32_t length = stream->readPackedUInt();
+    const uint32_t length = SkToU32(stream->readPackedUInt());
     if (length > 0) {
         string->resize(length);
         stream->read(string->writable_str(), length);