C++11 style fixups

Change-Id: I356d02338820bfef41a9e278c88dafc17cfe1cf9
diff --git a/libs/hwui/renderthread/CanvasContext.cpp b/libs/hwui/renderthread/CanvasContext.cpp
index 80c60d9..fcf6eb2 100644
--- a/libs/hwui/renderthread/CanvasContext.cpp
+++ b/libs/hwui/renderthread/CanvasContext.cpp
@@ -399,7 +399,7 @@
             continue;
         }
         fprintf(file, "\n");
-        for (int i = 0; i < FrameInfoIndex::kNumIndexes; i++) {
+        for (int i = 0; i < static_cast<int>(FrameInfoIndex::kNumIndexes); i++) {
             fprintf(file, "%" PRId64 ",", frame[i]);
         }
     }