Dex compiler: re-enable method pattern matching

The dex compiler's mechanism to detect simple methods and emit
streamlined code was disabled during the last big restructuring
(there was a question of how to make it useful for Portable as
well as Quick).  This CL does not address the Portable question,
but turns the optimization back on for Quick.

See b/9428200

Change-Id: I9f25b41219d7a243ec64efb18278e5a874766f4d
diff --git a/compiler/dex/mir_graph.h b/compiler/dex/mir_graph.h
index 9c63d9c..342d2a2 100644
--- a/compiler/dex/mir_graph.h
+++ b/compiler/dex/mir_graph.h
@@ -509,6 +509,14 @@
     return reg_location_[method_sreg_];
   }
 
+  bool IsSpecialCase() {
+    return special_case_ != kNoHandler;
+  }
+
+  SpecialCaseHandler GetSpecialCase() {
+    return special_case_;
+  }
+
   void BasicBlockCombine();
   void CodeLayout();
   void DumpCheckStats();
@@ -655,6 +663,7 @@
   int method_sreg_;
   unsigned int attributes_;
   Checkstats* checkstats_;
+  SpecialCaseHandler special_case_;
   ArenaAllocator* arena_;
 };