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

tools/DumpRecord.cpp

Index: tools/DumpRecord.cpp
diff --git a/tools/DumpRecord.cpp b/tools/DumpRecord.cpp
index 4f05fd46c108ef462a977667bd483c538d43716b..3c34231e18af8d891d5837949d688b7faefd59fc 100644
--- a/tools/DumpRecord.cpp
+++ b/tools/DumpRecord.cpp
@@ -105,7 +105,7 @@ void DumpRecord(const SkRecord& record,
                   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);
     }
 }