fix for GrAtlasTextContext occasionally crashes on mixed runs

src/gpu/GrAtlasTextContext.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 "GrBatch.h"
 #include "GrBatchFontCache.h"
@@ skipping 1264 matching lines @@
     // If the glyph is too large we fall back to paths
     if (glyph->fTooLargeForAtlas) {
         this->appendGlyphPath(blob, glyph, scaler, SkIntToScalar(vx), SkIntToScalar(vy));
         return;
     }
 
     GrMaskFormat format = glyph->fMaskFormat;
 
     PerSubRunInfo* subRun = &run.fSubRunInfo.back();
     if (run.fInitialized && subRun->fMaskFormat != format) {
-        subRun = &run.fSubRunInfo.push_back();
+        subRun = &run.push_back();
     }
 
     run.fInitialized = true;
 
     size_t vertexStride = get_vertex_stride(format);
 
     SkRect r;
     r.fLeft = SkIntToScalar(x);
     r.fTop = SkIntToScalar(y);
     r.fRight = r.fLeft + SkIntToScalar(width);
@@ skipping 995 matching lines @@
             gTextContext->createDrawTextBlob(rt, clip, grPaint, skPaint, viewMatrix, text,
                                              static_cast<size_t>(textLen), 0, 0, noClip));
 
     SkScalar transX = static_cast<SkScalar>(random->nextU());
     SkScalar transY = static_cast<SkScalar>(random->nextU());
     const GrAtlasTextBlob::Run::SubRunInfo& info = blob->fRuns[0].fSubRunInfo[0];
     return gTextContext->createBatch(blob, info, textLen, 0, 0, color, transX, transY, skPaint);
 }
 
 #endif