fix size_t/int warnings

src/core/SkReadBuffer.cpp

Index: src/core/SkReadBuffer.cpp
diff --git a/src/core/SkReadBuffer.cpp b/src/core/SkReadBuffer.cpp
index b60dee3ba6b860c88f1393d0cb4ecd168b697c12..b4bc87529ab5a5b1e1e620d2775f7e7a5f1dedf1 100644
--- a/src/core/SkReadBuffer.cpp
+++ b/src/core/SkReadBuffer.cpp
@@ -321,10 +321,10 @@ SkFlattenable* SkReadBuffer::readFlattenable(SkFlattenable::Type ft) {
     SkFlattenable* obj = NULL;
     uint32_t sizeRecorded = fReader.readU32();
     if (factory) {
-        uint32_t offset = fReader.offset();
+        size_t offset = fReader.offset();
         obj = (*factory)(*this);
         // check that we read the amount we expected
-        uint32_t sizeRead = fReader.offset() - offset;
+        size_t sizeRead = fReader.offset() - offset;
         if (sizeRecorded != sizeRead) {
             // we could try to fix up the offset...
             sk_throw();