ART: Some Quick cleanup

Make several fields const in CompilationUnit. May benefit some Mir2Lir
code that repeats tests, and in general immutability is good.

Remove compiler_internals.h and refactor some other headers to reduce
overly broad imports (and thus forced recompiles on changes).

Change-Id: I898405907c68923581373b5981d8a85d2e5d185a
diff --git a/compiler/dex/pass_driver.h b/compiler/dex/pass_driver.h
index 8a3eae1..632df38 100644
--- a/compiler/dex/pass_driver.h
+++ b/compiler/dex/pass_driver.h
@@ -18,13 +18,13 @@
 #define ART_COMPILER_DEX_PASS_DRIVER_H_
 
 #include <vector>
+
+#include "base/logging.h"
 #include "pass.h"
 #include "safe_map.h"
 
-// Forward Declarations.
-class Pass;
-class PassDriver;
 namespace art {
+
 /**
  * @brief Helper function to create a single instance of a given Pass and can be shared across
  * the threads.