Rename GlobalSynchronization to Locks

Also address some review comments in common_throws relating to
ToStr<InvokeType> and exception detail messages.

Change-Id: Ibf2c0f147689fa236d349bd7f01eed3c2522552b
diff --git a/src/space_bitmap.cc b/src/space_bitmap.cc
index 439e637..7a4c48d 100644
--- a/src/space_bitmap.cc
+++ b/src/space_bitmap.cc
@@ -174,7 +174,7 @@
 // class.
 static void WalkInstanceFields(SpaceBitmap* visited, SpaceBitmap::Callback* callback, Object* obj,
                                Class* klass, void* arg)
-    SHARED_LOCKS_REQUIRED(GlobalSynchronization::mutator_lock_) {
+    SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
   // Visit fields of parent classes first.
   Class* super = klass->GetSuperClass();
   if (super != NULL) {
@@ -199,7 +199,7 @@
 // For an unvisited object, visit it then all its children found via fields.
 static void WalkFieldsInOrder(SpaceBitmap* visited, SpaceBitmap::Callback* callback, Object* obj,
                               void* arg)
-    SHARED_LOCKS_REQUIRED(GlobalSynchronization::mutator_lock_) {
+    SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
   if (visited->Test(obj)) {
     return;
   }