Removes warnings generated by gcc and clang.



git-svn-id: http://skia.googlecode.com/svn/trunk@2651 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tests/ReadPixelsTest.cpp b/tests/ReadPixelsTest.cpp
index 5a6604a..026694f 100644
--- a/tests/ReadPixelsTest.cpp
+++ b/tests/ReadPixelsTest.cpp
@@ -324,12 +324,12 @@
             SkCanvas::kRGBA_Premul_Config8888,
             SkCanvas::kRGBA_Unpremul_Config8888,
         };
-        for (int rect = 0; rect < SK_ARRAY_COUNT(testRects); ++rect) {
+        for (size_t rect = 0; rect < SK_ARRAY_COUNT(testRects); ++rect) {
             const SkIRect& srcRect = testRects[rect];
             for (BitmapInit bmi = kFirstBitmapInit;
                  bmi < kBitmapInitCnt;
                  bmi = nextBMI(bmi)) {
-                for (int c = 0; c < SK_ARRAY_COUNT(gReadConfigs); ++c) {
+                for (size_t c = 0; c < SK_ARRAY_COUNT(gReadConfigs); ++c) {
                     SkCanvas::Config8888 config8888 = gReadConfigs[c];
                     SkBitmap bmp;
                     init_bitmap(&bmp, srcRect, bmi);