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/live_ranges_test.cc b/compiler/optimizing/live_ranges_test.cc
index b9ab290..7f67560 100644
--- a/compiler/optimizing/live_ranges_test.cc
+++ b/compiler/optimizing/live_ranges_test.cc
@@ -77,7 +77,7 @@
   ASSERT_EQ(2u, range->GetStart());
   // Last use is the return instruction.
   ASSERT_EQ(8u, range->GetEnd());
-  HBasicBlock* block = graph->GetBlock(1);
+  HBasicBlock* block = graph->GetBlocks()[1];
   ASSERT_TRUE(block->GetLastInstruction()->IsReturn());
   ASSERT_EQ(8u, block->GetLastInstruction()->GetLifetimePosition());
   ASSERT_TRUE(range->GetNext() == nullptr);
@@ -125,7 +125,7 @@
   ASSERT_EQ(2u, range->GetStart());
   // Last use is the return instruction.
   ASSERT_EQ(22u, range->GetEnd());
-  HBasicBlock* block = graph->GetBlock(3);
+  HBasicBlock* block = graph->GetBlocks()[3];
   ASSERT_TRUE(block->GetLastInstruction()->IsReturn());
   ASSERT_EQ(22u, block->GetLastInstruction()->GetLifetimePosition());
   ASSERT_TRUE(range->GetNext() == nullptr);