Remove DrawingMgr shims from GrContext

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 255 matching lines @@
         // the outside.
         maskDesc.fWidth = texture->width();
         maskDesc.fHeight = texture->height();
         SkAutoTUnref<GrTexture> maskTexture(
             context->textureProvider()->createApproxTexture(maskDesc));
         if (!maskTexture) {
             return false;
         }
 
         SkAutoTUnref<GrDrawContext> drawContext(
-                                            context->drawContext(maskTexture->asRenderTarget()));
+                               context->drawingMgr().drawContext(maskTexture->asRenderTarget()));
         if (drawContext) {
             GrPaint grPaint;
             grPaint.setPorterDuffXPFactory(SkXfermode::kSrc_Mode);
             SkRegion::Iterator iter(fRegion);
             drawContext->clear(nullptr, 0x0, true);
 
             while (!iter.done()) {
                 SkRect rect = SkRect::Make(iter.rect());
                 drawContext->drawRect(GrClip::WideOpen(), grPaint, inMatrix, rect);
                 iter.next();
@@ skipping 79 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