unsigned -> int for counts and indices in picture-related code

also, (C)

BUG=skia:

Review URL: https://codereview.chromium.org/1300163002
diff --git a/tests/RecorderTest.cpp b/tests/RecorderTest.cpp
index c41d634..b4bc58d 100644
--- a/tests/RecorderTest.cpp
+++ b/tests/RecorderTest.cpp
@@ -30,7 +30,7 @@
     int count() const { return fHistogram[T::kType]; }
 
     void apply(const SkRecord& record) {
-        for (unsigned i = 0; i < record.count(); i++) {
+        for (int i = 0; i < record.count(); i++) {
             record.visit<void>(i, *this);
         }
     }