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/quick/codegen_util.cc b/compiler/dex/quick/codegen_util.cc
index 630e294..9e9b39e 100644
--- a/compiler/dex/quick/codegen_util.cc
+++ b/compiler/dex/quick/codegen_util.cc
@@ -950,16 +950,13 @@
   /* Allocate Registers using simple local allocation scheme */
   SimpleRegAlloc();
 
-  //FIXME: re-enable by retrieving from mir_graph
-  SpecialCaseHandler special_case = kNoHandler;
-
-  if (special_case != kNoHandler) {
+  if (mir_graph_->IsSpecialCase()) {
       /*
        * Custom codegen for special cases.  If for any reason the
        * special codegen doesn't succeed, first_lir_insn_ will
        * set to NULL;
        */
-      SpecialMIR2LIR(special_case);
+      SpecialMIR2LIR(mir_graph_->GetSpecialCase());
     }
 
   /* Convert MIR to LIR, etc. */