fix size_t/int warnings

src/core/SkWriter32.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkReader32.h"
 #include "SkString.h"
 #include "SkWriter32.h"
@@ skipping 29 matching lines @@
     if (NULL == str) {
         str = "";
         len = 0;
     }
     if ((long)len < 0) {
         len = strlen(str);
     }
 
     // [ 4 byte len ] [ str ... ] [1 - 4 \0s]
     uint32_t* ptr = this->reservePad(sizeof(uint32_t) + len + 1);
-    *ptr = len;
+    *ptr = SkToU32(len);
     char* chars = (char*)(ptr + 1);
     memcpy(chars, str, len);
     chars[len] = '\0';
 }
 
 size_t SkWriter32::WriteStringSize(const char* str, size_t len) {
     if ((long)len < 0) {
         SkASSERT(str);
         len = strlen(str);
     }
@@ skipping 35 matching lines @@
             // prepare us to do copy on write, by pretending the data buffer
             // is external and size limited
             mutable_this.fData = buffer;
             mutable_this.fCapacity = fUsed;
             mutable_this.fExternal = buffer;
         }
         mutable_this.fSnapshot.reset(SkData::NewFromMalloc(buffer, fUsed));
     }
     return SkRef(fSnapshot.get()); // Take an extra ref for the caller.
 }