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/compiler/optimizing/instruction_simplifier.cc b/compiler/optimizing/instruction_simplifier.cc
index 8e0b414..5ac77a5 100644
--- a/compiler/optimizing/instruction_simplifier.cc
+++ b/compiler/optimizing/instruction_simplifier.cc
@@ -18,7 +18,7 @@
 
 #include "art_method-inl.h"
 #include "class_linker-inl.h"
-#include "class_root.h"
+#include "class_root-inl.h"
 #include "data_type-inl.h"
 #include "escape.h"
 #include "intrinsics.h"