Minor clean-up of thread status changes.

Eliminate the obsolete self != NULL test when acquiring the heap lock.
This should be redundant now that threads are added to the thread list
before they are able to allocate.

Switch to using a variable of the ThreadStatus type to store thread
status values rather than an ordinary int.

Change-Id: I8d30e69f20d5321a04f6b49322f13b3577d5a3c4
diff --git a/vm/alloc/Heap.c b/vm/alloc/Heap.c
index cc3fd72..1f36601 100644
--- a/vm/alloc/Heap.c
+++ b/vm/alloc/Heap.c
@@ -166,16 +166,9 @@
         ThreadStatus oldStatus;
 
         self = dvmThreadSelf();
-        if (self != NULL) {
-            oldStatus = dvmChangeStatus(self, THREAD_VMWAIT);
-        } else {
-            LOGI("ODD: waiting on heap lock, no self\n");
-            oldStatus = -1; // shut up gcc
-        }
+        oldStatus = dvmChangeStatus(self, THREAD_VMWAIT);
         dvmLockMutex(&gDvm.gcHeapLock);
-        if (self != NULL) {
-            dvmChangeStatus(self, oldStatus);
-        }
+        dvmChangeStatus(self, oldStatus);
     }
 
     return true;