Rename BitSetIterator.h to bitset_utils.h

BUG=angleproject:1814

Change-Id: I152ae13b6b7cf0ba72259967f0f124e199b20e07
Reviewed-on: https://chromium-review.googlesource.com/471826
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libANGLE/renderer/d3d/ProgramD3D.cpp b/src/libANGLE/renderer/d3d/ProgramD3D.cpp
index 07db179..c2f478a 100644
--- a/src/libANGLE/renderer/d3d/ProgramD3D.cpp
+++ b/src/libANGLE/renderer/d3d/ProgramD3D.cpp
@@ -8,7 +8,7 @@
 
 #include "libANGLE/renderer/d3d/ProgramD3D.h"
 
-#include "common/BitSetIterator.h"
+#include "common/bitset_utils.h"
 #include "common/utilities.h"
 #include "libANGLE/Framebuffer.h"
 #include "libANGLE/FramebufferAttachment.h"