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

also, (C)

BUG=skia:

Review URL: https://codereview.chromium.org/1300163002
diff --git a/tools/DumpRecord.cpp b/tools/DumpRecord.cpp
index 4f05fd4..3c34231 100644
--- a/tools/DumpRecord.cpp
+++ b/tools/DumpRecord.cpp
@@ -105,7 +105,7 @@
                   SkCanvas* canvas,
                   bool timeWithCommand) {
     Dumper dumper(canvas, record.count(), timeWithCommand);
-    for (unsigned i = 0; i < record.count(); i++) {
+    for (int i = 0; i < record.count(); i++) {
         record.visit<void>(i, dumper);
     }
 }