Update references to Blink's Platform API headers

chrome/renderer/printing/print_web_view_helper_mac.mm

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/renderer/printing/print_web_view_helper.h"
 
 #import <AppKit/AppKit.h>
 
 #include "base/logging.h"
 #include "base/mac/scoped_nsautorelease_pool.h"
 #include "base/metrics/histogram.h"
 #include "chrome/common/print_messages.h"
 #include "printing/metafile.h"
 #include "printing/metafile_impl.h"
 #include "printing/metafile_skia_wrapper.h"
 #include "printing/page_size_margins.h"
 #include "skia/ext/platform_device.h"
 #include "skia/ext/vector_canvas.h"
-#include "third_party/WebKit/Source/Platform/chromium/public/WebCanvas.h"
+#include "third_party/WebKit/public/platform/WebCanvas.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebFrame.h"
 
 namespace printing {
 
 using WebKit::WebFrame;
 
 void PrintWebViewHelper::PrintPageInternal(
     const PrintMsg_PrintPage_Params& params,
     const gfx::Size& canvas_size,
     WebFrame* frame) {
@@ skipping 108 matching lines @@
     }
     RenderPageContent(frame, page_number, canvas_area, content_area,
                       scale_factor, canvas_ptr);
   }
 
   // Done printing. Close the device context to retrieve the compiled metafile.
   metafile->FinishPage();
 }
 
 }  // namespace printing