Switch SkCodec to int for counts and indices

This matches other Skia APIs. size_t was adopted from blink/
GIFImageReader.

Change-Id: Ic83e59f0942f597c4fb834e623acd9886ad483fe
Reviewed-on: https://skia-review.googlesource.com/13274
Reviewed-by: Mike Reed <reed@google.com>
Reviewed-by: Matt Sarett <msarett@google.com>
Reviewed-by: Chris Blume <cblume@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>
diff --git a/tests/CodecTest.cpp b/tests/CodecTest.cpp
index ceafa15..5224054 100644
--- a/tests/CodecTest.cpp
+++ b/tests/CodecTest.cpp
@@ -1508,7 +1508,7 @@
 
     auto frameInfos = codec->getFrameInfo();
     SkCodec::Options opts;
-    for (size_t i = 0; i < frameInfos.size(); i++) {
+    for (int i = 0; static_cast<size_t>(i) < frameInfos.size(); i++) {
         opts.fFrameIndex = i;
         opts.fHasPriorFrame = frameInfos[i].fRequiredFrame == i - 1;
         auto result = codec->startIncrementalDecode(info, bm.getPixels(), bm.rowBytes(), &opts);