Compile-time tuning

Specialized the dataflow iterators and did a few other minor tweaks.
Showing ~5% compile-time improvement in a single-threaded environment;
less in multi-threaded (presumably because we're blocked by something
else).

Change-Id: I2e2ed58d881414b9fc97e04cd0623e188259afd2
diff --git a/compiler/dex/mir_dataflow.cc b/compiler/dex/mir_dataflow.cc
index 3a73717..addfd6b 100644
--- a/compiler/dex/mir_dataflow.cc
+++ b/compiler/dex/mir_dataflow.cc
@@ -1287,7 +1287,7 @@
   if (cu_->disable_opt & (1 << kPromoteRegs)) {
     return;
   }
-  AllNodesIterator iter(this, false /* not iterative */);
+  AllNodesIterator iter(this);
   for (BasicBlock* bb = iter.Next(); bb != NULL; bb = iter.Next()) {
     CountUses(bb);
   }
@@ -1331,7 +1331,7 @@
 
 void MIRGraph::VerifyDataflow() {
     /* Verify if all blocks are connected as claimed */
-  AllNodesIterator iter(this, false /* not iterative */);
+  AllNodesIterator iter(this);
   for (BasicBlock* bb = iter.Next(); bb != NULL; bb = iter.Next()) {
     VerifyPredInfo(bb);
   }