wire up new json code in skiaserve

tools/debugger/SkDebugCanvas.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkClipStack.h"
 #include "SkDebugCanvas.h"
 #include "SkDrawCommand.h"
@@ skipping 300 matching lines @@
 }
 
 const SkTDArray <SkDrawCommand*>& SkDebugCanvas::getDrawCommands() const {
     return fCommandVector;
 }
 
 SkTDArray <SkDrawCommand*>& SkDebugCanvas::getDrawCommands() {
     return fCommandVector;
 }
 
-Json::Value SkDebugCanvas::toJSON(UrlDataManager& urlDataManager) {
+Json::Value SkDebugCanvas::toJSON(UrlDataManager& urlDataManager, int n) {
     Json::Value result = Json::Value(Json::objectValue);
     result[SKDEBUGCANVAS_ATTRIBUTE_VERSION] = Json::Value(SKDEBUGCANVAS_VERSION);
     Json::Value commands = Json::Value(Json::arrayValue);
-    for (int i = 0; i < this->getSize(); i++) {
+    for (int i = 0; i < this->getSize() && i < n; i++) {
         commands[i] = this->getDrawCommandAt(i)->toJSON();
     }
     result[SKDEBUGCANVAS_ATTRIBUTE_COMMANDS] = commands;
     return result;
 }
 
 void SkDebugCanvas::updatePaintFilterCanvas() {
     if (!fOverdrawViz && !fOverrideFilterQuality) {
         fPaintFilterCanvas.reset(nullptr);
         return;
@@ skipping 294 matching lines @@
 }
 
 bool SkDebugCanvas::lastClipStackData(const SkPath& devPath) {
     if (fCalledAddStackData) {
         fClipStackData.appendf("<br>");
         addPathData(devPath, "pathOut");
         return true;
     }
     return false;
 }