Move implementations from class_root.h to -inl.h .

Make it possible to include the definition of enum ClassRoot
without pulling in a lot of other headers.

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Test: aosp_taimen-userdebug boots.
Change-Id: Ic90fdd70bfe0c5428a5c9a0d7901ea7e15b03488
diff --git a/runtime/thread.cc b/runtime/thread.cc
index e92e391..21b8d05 100644
--- a/runtime/thread.cc
+++ b/runtime/thread.cc
@@ -56,7 +56,7 @@
 #include "base/to_str.h"
 #include "base/utils.h"
 #include "class_linker-inl.h"
-#include "class_root.h"
+#include "class_root-inl.h"
 #include "debugger.h"
 #include "dex/descriptors_names.h"
 #include "dex/dex_file-inl.h"