Fix drawVertices() on GPU when texs=colors=shaders=indices=null

src/gpu/SkGpuDevice.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkGpuDevice.h"
 
 #include "effects/GrBicubicEffect.h"
@@ skipping 1604 matching lines @@
                               const uint16_t indices[], int indexCount,
                               const SkPaint& paint) {
     CHECK_SHOULD_DRAW(draw, false);
 
     GR_CREATE_TRACE_MARKER_CONTEXT("SkGpuDevice::drawVertices", fContext);
     
     const uint16_t* outIndices;
     SkAutoTDeleteArray<uint16_t> outAlloc(NULL);
     GrPrimitiveType primType;
     GrPaint grPaint;
-    
+
     // If both textures and vertex-colors are NULL, strokes hairlines with the paint's color.
     if ((NULL == texs || NULL == paint.getShader()) && NULL == colors) {
         
         texs = NULL;
         
         SkPaint copy(paint);
         copy.setStyle(SkPaint::kStroke_Style);
         copy.setStrokeWidth(0);
         
         // we ignore the shader if texs is null.
         SkPaint2GrPaintNoShader(this->context(), copy, SkColor2GrColor(copy.getColor()),
                                 NULL == colors, &grPaint);
 
         primType = kLines_GrPrimitiveType;
         int triangleCount = 0;
+        int n = (NULL == indices) ? vertexCount : indexCount;
         switch (vmode) {
             case SkCanvas::kTriangles_VertexMode:
-                triangleCount = indexCount / 3;
+                triangleCount = n / 3;
                 break;
             case SkCanvas::kTriangleStrip_VertexMode:
             case SkCanvas::kTriangleFan_VertexMode:
-                triangleCount = indexCount - 2;
+                triangleCount = n - 2;
                 break;
         }
         
         VertState       state(vertexCount, indices, indexCount);
         VertState::Proc vertProc = state.chooseProc(vmode);
         
         //number of indices for lines per triangle with kLines
         indexCount = triangleCount * 6;
         
         outAlloc.reset(SkNEW_ARRAY(uint16_t, indexCount));
@@ skipping 465 matching lines @@
     }
 
     return true;
 }
 
 SkImageFilter::UniqueIDCache* SkGpuDevice::getImageFilterCache() {
     // We always return a transient cache, so it is freed after each
     // filter traversal.
     return SkImageFilter::UniqueIDCache::Create(kDefaultImageFilterCacheSize);
 }