Use observed pointers in CPDFSDK_AnnotIterator.

Rename to CPDFSDK_AnnotIteration, as it is now an ordered set of
annots, and not the iterator itself.

Review-Url: https://codereview.chromium.org/2626073005
diff --git a/BUILD.gn b/BUILD.gn
index 9a5c29c..ebb821c 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -74,8 +74,8 @@
     "fpdfsdk/cpdfsdk_annot.h",
     "fpdfsdk/cpdfsdk_annothandlermgr.cpp",
     "fpdfsdk/cpdfsdk_annothandlermgr.h",
-    "fpdfsdk/cpdfsdk_annotiterator.cpp",
-    "fpdfsdk/cpdfsdk_annotiterator.h",
+    "fpdfsdk/cpdfsdk_annotiteration.cpp",
+    "fpdfsdk/cpdfsdk_annotiteration.h",
     "fpdfsdk/cpdfsdk_baannot.cpp",
     "fpdfsdk/cpdfsdk_baannot.h",
     "fpdfsdk/cpdfsdk_baannothandler.cpp",