fix more 64bit warnings

BUG=skia:

Review URL: https://codereview.chromium.org/147683003

git-svn-id: http://skia.googlecode.com/svn/trunk@13190 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/samplecode/SampleComplexClip.cpp b/samplecode/SampleComplexClip.cpp
index 30f94f7..0d613ec 100644
--- a/samplecode/SampleComplexClip.cpp
+++ b/samplecode/SampleComplexClip.cpp
@@ -96,7 +96,7 @@
 
         for (int invA = 0; invA < 2; ++invA) {
             for (size_t op = 0; op < SK_ARRAY_COUNT(gOps); ++op) {
-                int idx = invA * SK_ARRAY_COUNT(gOps) + op;
+                size_t idx = invA * SK_ARRAY_COUNT(gOps) + op;
                 if (!(idx % 3)) {
                     canvas->restore();
                     canvas->translate(0, SkIntToScalar(250));