Fix signed/unsigned comparison in PictureTest.cpp



git-svn-id: http://skia.googlecode.com/svn/trunk@7092 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tests/PictureTest.cpp b/tests/PictureTest.cpp
index 26b1f56..da8d13a 100644
--- a/tests/PictureTest.cpp
+++ b/tests/PictureTest.cpp
@@ -133,7 +133,7 @@
                 uint32_t index = SkGetPackedR32(pmc);
                 SkASSERT(SkGetPackedG32(pmc) == index);
                 SkASSERT(SkGetPackedB32(pmc) == index);
-                SkASSERT(index < count);
+                SkASSERT(static_cast<int>(index) < count);
                 bitarray |= 1 << index;
             }
         }