Add a new control flow simplifier.

Run it in the dead code elimination phase, as it relates to
creating dead branches.

From 0.04 to 0.07% less code size framework/gms/docs/fb (70K saved on fb)
3%-5% runtime performance improvements on Richards/DeltaBlue/Ritz.
Compile-time is mixed, so in the noise (from 2% slower to 1% faster).

test:611-checker-simplify-if

Change-Id: Ife8b7882d57b5481f5ca9dc163beba655d7e78bf
diff --git a/compiler/optimizing/optimizing_compiler_stats.h b/compiler/optimizing/optimizing_compiler_stats.h
index 9cc6ea4..c8d1ce0 100644
--- a/compiler/optimizing/optimizing_compiler_stats.h
+++ b/compiler/optimizing/optimizing_compiler_stats.h
@@ -65,6 +65,7 @@
   kInlinedInvokeVirtualOrInterface,
   kImplicitNullCheckGenerated,
   kExplicitNullCheckGenerated,
+  kSimplifyIf,
   kLastStat
 };
 
@@ -143,6 +144,7 @@
       case kInlinedInvokeVirtualOrInterface: name = "InlinedInvokeVirtualOrInterface"; break;
       case kImplicitNullCheckGenerated: name = "ImplicitNullCheckGenerated"; break;
       case kExplicitNullCheckGenerated: name = "ExplicitNullCheckGenerated"; break;
+      case kSimplifyIf: name = "SimplifyIf"; break;
 
       case kLastStat:
         LOG(FATAL) << "invalid stat "