Limit lifetime of GrDrawContext objects

src/effects/SkAlphaThresholdFilter.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 "SkAlphaThresholdFilter.h"
 #include "SkBitmap.h"
 #include "SkReadBuffer.h"
@@ skipping 259 matching lines @@
         // Add one pixel of border to ensure that clamp mode will be all zeros
         // the outside.
         maskDesc.fWidth = texture->width();
         maskDesc.fHeight = texture->height();
         SkAutoTUnref<GrTexture> maskTexture(
             context->textureProvider()->createApproxTexture(maskDesc));
         if (!maskTexture) {
             return false;
         }
 
-        GrDrawContext* drawContext = context->drawContext();
+        SkAutoTUnref<GrDrawContext> drawContext(context->drawContext());
         if (drawContext) {
             GrPaint grPaint;
             grPaint.setPorterDuffXPFactory(SkXfermode::kSrc_Mode);
             SkRegion::Iterator iter(fRegion);
             drawContext->clear(maskTexture->asRenderTarget(), nullptr, 0x0, true);
 
             while (!iter.done()) {
                 SkRect rect = SkRect::Make(iter.rect());
                 drawContext->drawRect(maskTexture->asRenderTarget(), GrClip::WideOpen(), grPaint,
                                       in_matrix, rect);
@@ skipping 81 matching lines @@
 }
 
 #ifndef SK_IGNORE_TO_STRING
 void SkAlphaThresholdFilterImpl::toString(SkString* str) const {
     str->appendf("SkAlphaThresholdImageFilter: (");
     str->appendf("inner: %f outer: %f", fInnerThreshold, fOuterThreshold);
     str->append(")");
 }
 #endif