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

BUG=skia:
R=mtklein@google.com

Author: reed@google.com

Review URL: https://codereview.chromium.org/147053003

git-svn-id: http://skia.googlecode.com/svn/trunk@13178 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/core/SkDebug.cpp b/src/core/SkDebug.cpp
index 2a04b30..7723522 100644
--- a/src/core/SkDebug.cpp
+++ b/src/core/SkDebug.cpp
@@ -41,4 +41,9 @@
     return (uint32_t)x;
 }
 
+int SkToInt(intmax_t x) {
+    SkASSERT((int)x == x);
+    return (int)x;
+}
+
 #endif