Add DCHECKs to ArenaVector and ScopedArenaVector.

Implement dchecked_vector<> template that DCHECK()s element
access and insert()/emplace()/erase() positions. Change the
ArenaVector<> and ScopedArenaVector<> aliases to use the new
template instead of std::vector<>. Remove DCHECK()s that
have now become unnecessary from the Optimizing compiler.

Change-Id: Ib8506bd30d223f68f52bd4476c76d9991acacadc
diff --git a/compiler/optimizing/codegen_test.cc b/compiler/optimizing/codegen_test.cc
index 5fc305c..22f227c 100644
--- a/compiler/optimizing/codegen_test.cc
+++ b/compiler/optimizing/codegen_test.cc
@@ -561,7 +561,7 @@
   ASSERT_FALSE(equal->NeedsMaterialization());
 
   auto hook_before_codegen = [](HGraph* graph_in) {
-    HBasicBlock* block = graph_in->GetEntryBlock()->GetSuccessor(0);
+    HBasicBlock* block = graph_in->GetEntryBlock()->GetSuccessors()[0];
     HParallelMove* move = new (graph_in->GetArena()) HParallelMove(graph_in->GetArena());
     block->InsertInstructionBefore(move, block->GetLastInstruction());
   };
@@ -667,7 +667,7 @@
     code_block->AddInstruction(&ret);
 
     auto hook_before_codegen = [](HGraph* graph_in) {
-      HBasicBlock* block = graph_in->GetEntryBlock()->GetSuccessor(0);
+      HBasicBlock* block = graph_in->GetEntryBlock()->GetSuccessors()[0];
       HParallelMove* move = new (graph_in->GetArena()) HParallelMove(graph_in->GetArena());
       block->InsertInstructionBefore(move, block->GetLastInstruction());
     };
@@ -733,7 +733,7 @@
     if_false_block->AddInstruction(&ret_ge);
 
     auto hook_before_codegen = [](HGraph* graph_in) {
-      HBasicBlock* block = graph_in->GetEntryBlock()->GetSuccessor(0);
+      HBasicBlock* block = graph_in->GetEntryBlock()->GetSuccessors()[0];
       HParallelMove* move = new (graph_in->GetArena()) HParallelMove(graph_in->GetArena());
       block->InsertInstructionBefore(move, block->GetLastInstruction());
     };