Minor cleanup of clip mask manager

src/gpu/GrDrawingManager.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrAtlasTextContext.h"
 #include "GrDrawContext.h"
 #include "GrDrawingManager.h"
@@ skipping 13 matching lines @@
     delete fNVPRTextContext;
     fNVPRTextContext = nullptr;
 
     for (int i = 0; i < kNumPixelGeometries; ++i) {
         delete fTextContexts[i][0];
         fTextContexts[i][0] = nullptr;
         delete fTextContexts[i][1];
         fTextContexts[i][1] = nullptr;
     }
 
-    SkSafeSetNull(fPathRendererChain);
+    delete fPathRendererChain;
+    fPathRendererChain = nullptr;
     SkSafeSetNull(fSoftwarePathRenderer);
 }
 
 GrDrawingManager::~GrDrawingManager() {
     this->cleanup();
 }
 
 void GrDrawingManager::abandon() {
     fAbandoned = true;
     this->cleanup();
 }
 
 void GrDrawingManager::freeGpuResources() {
     // a path renderer may be holding onto resources
-    SkSafeSetNull(fPathRendererChain);
+    delete fPathRendererChain;
+    fPathRendererChain = nullptr;
     SkSafeSetNull(fSoftwarePathRenderer);
 }
 
 void GrDrawingManager::reset() {
     for (int i = 0; i < fDrawTargets.count(); ++i) {
         fDrawTargets[i]->reset();
     }
 }
 
 void GrDrawingManager::flush() {
@@ skipping 91 matching lines @@
 }
 
 GrDrawContext* GrDrawingManager::drawContext(GrRenderTarget* rt,
                                              const SkSurfaceProps* surfaceProps) {
     if (this->abandoned()) {
         return nullptr;
     }
 
     return new GrDrawContext(this, rt, surfaceProps);
 }