Use known strides instead of input args when possible.

BUG=6892059

Change-Id: I15b3726624ff0eeca5e30aaa6de928f1c9912471
diff --git a/lib/Renderscript/RSCompiler.cpp b/lib/Renderscript/RSCompiler.cpp
index 7944c86..7ba1cff 100644
--- a/lib/Renderscript/RSCompiler.cpp
+++ b/lib/Renderscript/RSCompiler.cpp
@@ -104,7 +104,8 @@
   }
 
   // Expand ForEach on CPU path to reduce launch overhead.
-  rs_passes.add(createRSForEachExpandPass(info->getExportForeachFuncs()));
+  rs_passes.add(createRSForEachExpandPass(info->getExportForeachFuncs(),
+                                          /* pEnableStepOpt */ true));
 
   // Execute the pass.
   rs_passes.run(module);