Introduce a class to implement optimization passes.

- Add art::HOptimization.
- Rename art::ConstantPropagation to art::HConstantFolding in
  compiler/optimizing/constant_folding.h to avoid name
  clashes with a class of the same name in
  compiler/dex/post_opt_passes.h.
- Rename art::DeadCodeElimination to
  art::HDeadCodeElimination for consistency reasons.
- Have art::HDeadCodeElimination and art::HConstantFolding
  derive from art::HOptimization.
- Start to use these optimizations in
  art:OptimizingCompiler::TryCompile.

Change-Id: Iaab350c122d87b2333b3760312b15c0592d7e010
diff --git a/compiler/optimizing/dead_code_elimination.cc b/compiler/optimizing/dead_code_elimination.cc
index fe2adc7..5518851 100644
--- a/compiler/optimizing/dead_code_elimination.cc
+++ b/compiler/optimizing/dead_code_elimination.cc
@@ -20,7 +20,7 @@
 
 namespace art {
 
-void DeadCodeElimination::Run() {
+void HDeadCodeElimination::Run() {
   // Process basic blocks in post-order in the dominator tree, so that
   // a dead instruction depending on another dead instruction is
   // removed.