Add Drawing Manager guards against re-entrant flushes

src/gpu/GrDrawingManager.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrDrawingManager_DEFINED
 #define GrDrawingManager_DEFINED
 
@@ skipping 42 matching lines @@
     static bool ProgramUnitTest(GrContext* context, int maxStages);
 
 private:
     GrDrawingManager(GrContext* context, const GrDrawTarget::Options& optionsForDrawTargets)
         : fContext(context)
         , fOptionsForDrawTargets(optionsForDrawTargets)
         , fAbandoned(false)
         , fNVPRTextContext(nullptr)
         , fPathRendererChain(nullptr)
         , fSoftwarePathRenderer(nullptr)
-        , fFlushState(context->getGpu(), context->resourceProvider()) {
+        , fFlushState(context->getGpu(), context->resourceProvider())
+        , fFlushing(false) {
         sk_bzero(fTextContexts, sizeof(fTextContexts));
     }
 
     void abandon();
     void cleanup();
     void reset();
     void flush();
 
     friend class GrContext;  // for access to: ctor, abandon, reset & flush
 
     static const int kNumPixelGeometries = 5; // The different pixel geometries
     static const int kNumDFTOptions = 2;      // DFT or no DFT
 
     GrContext*                  fContext;
     GrDrawTarget::Options       fOptionsForDrawTargets;
 
     bool                        fAbandoned;
     SkTDArray<GrDrawTarget*>    fDrawTargets;
 
     GrTextContext*              fNVPRTextContext;
     GrTextContext*              fTextContexts[kNumPixelGeometries][kNumDFTOptions];
 
     GrPathRendererChain*        fPathRendererChain;
     GrSoftwarePathRenderer*     fSoftwarePathRenderer;
 
     GrBatchFlushState           fFlushState;
+    bool                        fFlushing;
 };
 
 #endif