Remove unnecessary includes in src/pdf/

src/pdf/SkPDFCanon.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 SkPDFCanon_DEFINED
 #define SkPDFCanon_DEFINED
 
 #include "SkPDFGraphicState.h"
 #include "SkPDFShader.h"
 #include "SkPixelSerializer.h"
 #include "SkTDArray.h"
 #include "SkTHash.h"
 #include "SkBitmapKey.h"
 
 class SkPDFFont;
-class SkPaint;
-class SkImage;
 
 /**
  *  The SkPDFCanon canonicalizes objects across PDF pages
  *  (SkPDFDevices) and across draw calls.
  *
  *  The PDF backend works correctly if:
  *  -  There is no more than one SkPDFCanon for each thread.
  *  -  Every SkPDFDevice is given a pointer to a SkPDFCanon on creation.
  *  -  All SkPDFDevices in a document share the same SkPDFCanon.
  *  The SkPDFDocument class makes this happen by owning a single
@@ skipping 79 matching lines @@
 
     // TODO(halcanary): make SkTHashMap<K, sk_sp<V>> work correctly.
     SkTHashMap<SkBitmapKey, SkPDFObject*> fPDFBitmapMap;
 
     sk_sp<SkPixelSerializer> fPixelSerializer;
     sk_sp<SkPDFStream> fInvertFunction;
     sk_sp<SkPDFDict> fNoSmaskGraphicState;
     sk_sp<SkPDFArray> fRangeObject;
 };
 #endif  // SkPDFCanon_DEFINED