be sure to unlock the discardablememory before deleting it

src/lazy/SkDiscardableMemoryPool.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkDiscardableMemoryPool.h"
 #include "SkOnce.h"
 
@@ skipping 29 matching lines @@
     , fLocked(true)
     , fPointer(pointer)
     , fBytes(bytes) {
     SkASSERT(fPool != NULL);
     SkASSERT(fPointer != NULL);
     SkASSERT(fBytes > 0);
     fPool->ref();
 }
 
 SkPoolDiscardableMemory::~SkPoolDiscardableMemory() {
+    SkASSERT(!fLocked); // contract for SkDiscardableMemory
     fPool->free(this);
     fPool->unref();
 }
 
 bool SkPoolDiscardableMemory::lock() {
+    SkASSERT(!fLocked); // contract for SkDiscardableMemory
     return fPool->lock(this);
 }
 
 void* SkPoolDiscardableMemory::data() {
-    return fLocked ? fPointer : NULL;
+    SkASSERT(fLocked); // contract for SkDiscardableMemory
+    return fPointer;
 }
 
 void SkPoolDiscardableMemory::unlock() {
+    SkASSERT(fLocked); // contract for SkDiscardableMemory
     fPool->unlock(this);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 
 SkDiscardableMemoryPool::SkDiscardableMemoryPool(size_t budget,
                                                  SkBaseMutex* mutex)
     : fMutex(mutex)
     , fBudget(budget)
     , fUsed(0) {
@@ skipping 121 matching lines @@
 }
 SkDiscardableMemoryPool* SkGetGlobalDiscardableMemoryPool() {
     static SkDiscardableMemoryPool* gPool(NULL);
     SK_DECLARE_STATIC_ONCE(create_pool_once);
     SkOnce(&create_pool_once, create_pool, &gPool);
     SkASSERT(NULL != gPool);
     return gPool;
 }
 
 ////////////////////////////////////////////////////////////////////////////////