ART: Run GraphChecker after Builder and SsaBuilder

This patch refactors the way GraphChecker is invoked, utilizing the
same scoping mechanism as pass timing and graph visualizer. Therefore,
GraphChecker will now run not just after instances of HOptimization
but after the builders and reg alloc, too.

Change-Id: I8173b98b79afa95e1fcbf3ac9630a873d7f6c1d4
diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index 581645f..0f5b1ab 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -160,6 +160,8 @@
   const GrowableArray<HBasicBlock*>& GetBlocks() const { return blocks_; }
   HBasicBlock* GetBlock(size_t id) const { return blocks_.Get(id); }
 
+  bool IsInSsaForm() const { return in_ssa_form_; }
+
   HBasicBlock* GetEntryBlock() const { return entry_block_; }
   HBasicBlock* GetExitBlock() const { return exit_block_; }
   bool HasExitBlock() const { return exit_block_ != nullptr; }