Support running without a boot image.

Bug: 17000769

Change-Id: I6404d5050c8a2f4ee6e70d58532eb25ee9de248e
diff --git a/runtime/runtime.h b/runtime/runtime.h
index 34ccdcb..784241e 100644
--- a/runtime/runtime.h
+++ b/runtime/runtime.h
@@ -107,7 +107,11 @@
   }
 
   bool IsDex2OatEnabled() const {
-    return dex2oat_enabled_;
+    return dex2oat_enabled_ && IsImageDex2OatEnabled();
+  }
+
+  bool IsImageDex2OatEnabled() const {
+    return image_dex2oat_enabled_;
   }
 
   CompilerCallbacks* GetCompilerCallbacks() {
@@ -509,6 +513,7 @@
   bool is_concurrent_gc_enabled_;
   bool is_explicit_gc_disabled_;
   bool dex2oat_enabled_;
+  bool image_dex2oat_enabled_;
 
   std::string compiler_executable_;
   std::string patchoat_executable_;