ART: Clean up ClassLinker

Try to clean up and simplify ClassLinker.

Move dex_lock to Locks. Remove dead code. Move single-use
code to user. Hide implementation details from header.

Test: m test-art-host
Change-Id: I58150fa9c2a9524f8304370270c2197d655cb3a8
diff --git a/runtime/base/mutex.cc b/runtime/base/mutex.cc
index 6665f95..ce452cb 100644
--- a/runtime/base/mutex.cc
+++ b/runtime/base/mutex.cc
@@ -67,6 +67,7 @@
 Uninterruptible Roles::uninterruptible_;
 ReaderWriterMutex* Locks::jni_globals_lock_ = nullptr;
 Mutex* Locks::jni_weak_globals_lock_ = nullptr;
+ReaderWriterMutex* Locks::dex_lock_ = nullptr;
 
 struct AllMutexData {
   // A guard for all_mutexes_ that's not a mutex (Mutexes must CAS to acquire and busy wait).
@@ -961,6 +962,7 @@
     DCHECK(thread_suspend_count_lock_ != nullptr);
     DCHECK(trace_lock_ != nullptr);
     DCHECK(unexpected_signal_lock_ != nullptr);
+    DCHECK(dex_lock_ != nullptr);
   } else {
     // Create global locks in level order from highest lock level to lowest.
     LockLevel current_lock_level = kInstrumentEntrypointsLock;
@@ -1039,6 +1041,10 @@
       modify_ldt_lock_ = new Mutex("modify_ldt lock", current_lock_level);
     }
 
+    UPDATE_CURRENT_LOCK_LEVEL(kDexLock);
+    DCHECK(dex_lock_ == nullptr);
+    dex_lock_ = new ReaderWriterMutex("ClassLinker dex lock", current_lock_level);
+
     UPDATE_CURRENT_LOCK_LEVEL(kOatFileManagerLock);
     DCHECK(oat_file_manager_lock_ == nullptr);
     oat_file_manager_lock_ = new ReaderWriterMutex("OatFile manager lock", current_lock_level);