ART: Some runtime cleanup

Use an enum for the compiler-callback mode.

Refactor and remove some unnecessary includes in runtime.h.

Change-Id: If2245fa470171311b8e05b677cf6bb28f209585a
diff --git a/compiler/dex/quick_compiler_callbacks.h b/compiler/dex/quick_compiler_callbacks.h
index 56706e3..d692d26 100644
--- a/compiler/dex/quick_compiler_callbacks.h
+++ b/compiler/dex/quick_compiler_callbacks.h
@@ -28,8 +28,8 @@
   public:
     QuickCompilerCallbacks(VerificationResults* verification_results,
                            DexFileToMethodInlinerMap* method_inliner_map,
-                           bool boot_image)
-        : CompilerCallbacks(boot_image), verification_results_(verification_results),
+                           CompilerCallbacks::CallbackMode mode)
+        : CompilerCallbacks(mode), verification_results_(verification_results),
           method_inliner_map_(method_inliner_map) {
       CHECK(verification_results != nullptr);
       CHECK(method_inliner_map != nullptr);