Add assert that memory pool is empty when GrTextBlobCache frees

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 "GrDrawContext.h"
 #include "GrDrawingManager.h"
 #include "GrDrawTarget.h"
 #include "GrResourceProvider.h"
 #include "GrSoftwarePathRenderer.h"
 #include "SkTTopoSort.h"
 
 #include "text/GrAtlasTextContext.h"
 #include "text/GrStencilAndCoverTextContext.h"
 
 void GrDrawingManager::cleanup() {
     for (int i = 0; i < fDrawTargets.count(); ++i) {
         fDrawTargets[i]->makeClosed();  // no drawTarget should receive a new command after this
         fDrawTargets[i]->clearRT();
 
+        // We shouldn't need to do this, but it turns out some clients still hold onto drawtargets
+        // after a cleanup
+        fDrawTargets[i]->reset();
         fDrawTargets[i]->unref();
     }
 
     fDrawTargets.reset();
 
     delete fNVPRTextContext;
     fNVPRTextContext = nullptr;
 
     for (int i = 0; i < kNumPixelGeometries; ++i) {
         delete fTextContexts[i][0];
@@ skipping 161 matching lines @@
 }
 
 GrDrawContext* GrDrawingManager::drawContext(GrRenderTarget* rt,
                                              const SkSurfaceProps* surfaceProps) {
     if (this->abandoned()) {
         return nullptr;
     }
 
     return new GrDrawContext(this, rt, surfaceProps);
 }