SkPDF: add canon assert before adding code that might break it

src/pdf/SkPDFDocument.h

 
 /*
  * Copyright 2010 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef SkPDFDocument_DEFINED
 #define SkPDFDocument_DEFINED
 
 #include "SkAdvancedTypefaceMetrics.h"
 #include "SkTDArray.h"
 
 class SkPDFDevice;
 class SkWStream;
 
 namespace SkPDFDocument {
 /**
  *  Assemble pages together and generate a PDF document file.
  *
  *  Output the PDF to the passed stream.  It is an error to call this (it
  *  will return false and not modify stream) if pageDevices is empty.
  *  No device pointer can be NULL.
  *
  *  @param pageDevices An array of pages, in order.  All pages
  *                     should be created using the same SkPDFCanon.
- *                     TODO(halcanary): ASSERT this condition.
  *  @param SkWStream   The writable output stream to send the PDF to.
  */
 bool EmitPDF(const SkTDArray<SkPDFDevice*>& pageDevices, SkWStream*);
 
 /** Get the count of unique font types used in the given pages.
  */
 void GetCountOfFontTypes(const SkTDArray<SkPDFDevice*>& pageDevices,
                          int counts[SkAdvancedTypefaceMetrics::kOther_Font + 1],
                          int* notSubsettableCount,
                          int* notEmbedddableCount);
 }
 
 #endif