Add a compilation tracing mechanism to the new compiler.

Code mostly imported from: https://android-review.googlesource.com/#/c/81653/.

Change-Id: I150fe942be0fb270e03fabb19032180f7a065d13
diff --git a/compiler/optimizing/graph_visualizer.h b/compiler/optimizing/graph_visualizer.h
new file mode 100644
index 0000000..433d55d
--- /dev/null
+++ b/compiler/optimizing/graph_visualizer.h
@@ -0,0 +1,63 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ART_COMPILER_OPTIMIZING_GRAPH_VISUALIZER_H_
+#define ART_COMPILER_OPTIMIZING_GRAPH_VISUALIZER_H_
+
+#include "utils/allocation.h"
+
+namespace art {
+
+class DexCompilationUnit;
+class HGraph;
+
+/**
+ * If enabled, emits compilation information suitable for the c1visualizer tool
+ * and IRHydra.
+ * Currently only works if the compiler is single threaded.
+ */
+class HGraphVisualizer : public ValueObject {
+ public:
+  /**
+   * If output is not null, and the method name of the dex compilation
+   * unit contains `string_filter`, the compilation information will be
+   * emitted.
+   */
+  HGraphVisualizer(std::ostream* output,
+                   HGraph* graph,
+                   const char* string_filter,
+                   const DexCompilationUnit& cu);
+
+  /**
+   * If this visualizer is enabled, emit the compilation information
+   * in `output_`.
+   */
+  void DumpGraph(const char* pass_name);
+
+ private:
+  std::ostream* const output_;
+  HGraph* const graph_;
+
+  // Is true when `output_` is not null, and the compiled method's name
+  // contains the string_filter given in the constructor.
+  bool is_enabled_;
+
+  DISALLOW_COPY_AND_ASSIGN(HGraphVisualizer);
+};
+
+}  // namespace art
+
+#endif  // ART_COMPILER_OPTIMIZING_GRAPH_VISUALIZER_H_