ART: Fix tidy warnings

Switch to char versions of find variants.

Add "explicit" constructor variants or refactor and
remove defaults.

Use const references.

Bug: 32619234
Test: m test-art-host
Change-Id: I970cc2f47d6cf8f0c74104b994b075b2fafb3d45
diff --git a/compiler/optimizing/constant_folding.h b/compiler/optimizing/constant_folding.h
index e10b1d6..05c6df4 100644
--- a/compiler/optimizing/constant_folding.h
+++ b/compiler/optimizing/constant_folding.h
@@ -39,8 +39,7 @@
  */
 class HConstantFolding : public HOptimization {
  public:
-  HConstantFolding(HGraph* graph, const char* name = kConstantFoldingPassName)
-      : HOptimization(graph, name) {}
+  HConstantFolding(HGraph* graph, const char* name) : HOptimization(graph, name) {}
 
   void Run() OVERRIDE;