Remove ArtCode.

- Instead use OatQuickMethodHeader.
- Various cleanups now that we don't have all those
  ArtMethod -> ArtCode -> OatQuickMethodHeader indirections.

As a consequence of this cleanup, exception handling got a bit
faster.

ParserCombinators benchmark (exception intensive) on x64: (lower is better)
Before:
ParserCombinators(RunTime): 1062500.0 us.
After:
ParserCombinators(RunTime): 833000.0 us.

Change-Id: Idac917b6f1b0dc254ad68fb3781cd61bccadb0f3
diff --git a/runtime/entrypoints/entrypoint_utils.h b/runtime/entrypoints/entrypoint_utils.h
index 171ace2..0469ee6 100644
--- a/runtime/entrypoints/entrypoint_utils.h
+++ b/runtime/entrypoints/entrypoint_utils.h
@@ -20,7 +20,6 @@
 #include <jni.h>
 #include <stdint.h>
 
-#include "art_code.h"
 #include "base/macros.h"
 #include "base/mutex.h"
 #include "dex_instruction.h"
@@ -40,6 +39,7 @@
 
 class ArtField;
 class ArtMethod;
+class OatQuickMethodHeader;
 class ScopedObjectAccessAlreadyRunnable;
 class Thread;
 
@@ -185,10 +185,6 @@
                                      Runtime::CalleeSaveType type,
                                      bool do_caller_check = false);
 
-inline ArtCode GetCallingCodeFrom(ArtMethod** sp) {
-  return ArtCode(sp);
-}
-
 }  // namespace art
 
 #endif  // ART_RUNTIME_ENTRYPOINTS_ENTRYPOINT_UTILS_H_