Don't let rounding prematurely influence document size when printing

components/printing/renderer/print_web_view_helper.cc

 // 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 "components/printing/renderer/print_web_view_helper.h"
 
 #include <stddef.h>
 #include <stdint.h>
 #include <string>
 #include <utility>
@@ skipping 109 matching lines @@
          params.document_cookie != 0;
 }
 
 PrintMsg_Print_Params GetCssPrintParams(
     blink::WebLocalFrame* frame,
     int page_index,
     const PrintMsg_Print_Params& page_params) {
   PrintMsg_Print_Params page_css_params = page_params;
   int dpi = GetDPI(&page_params);
 
-  blink::WebSize page_size_in_pixels(
-      ConvertUnit(page_params.page_size.width(), dpi, kPixelsPerInch),
-      ConvertUnit(page_params.page_size.height(), dpi, kPixelsPerInch));
+  blink::WebFloatSize page_size_in_pixels(
+      ConvertUnitDouble(page_params.page_size.width(), dpi, kPixelsPerInch),
+      ConvertUnitDouble(page_params.page_size.height(), dpi, kPixelsPerInch));
   int margin_top_in_pixels =
       ConvertUnit(page_params.margin_top, dpi, kPixelsPerInch);
   int margin_right_in_pixels = ConvertUnit(
       page_params.page_size.width() -
       page_params.content_size.width() - page_params.margin_left,
       dpi, kPixelsPerInch);
   int margin_bottom_in_pixels = ConvertUnit(
       page_params.page_size.height() -
       page_params.content_size.height() - page_params.margin_top,
       dpi, kPixelsPerInch);
   int margin_left_in_pixels = ConvertUnit(
       page_params.margin_left,
       dpi, kPixelsPerInch);
 
-  blink::WebSize original_page_size_in_pixels = page_size_in_pixels;
-
   if (frame) {
     frame->pageSizeAndMarginsInPixels(page_index,
                                       page_size_in_pixels,
                                       margin_top_in_pixels,
                                       margin_right_in_pixels,
                                       margin_bottom_in_pixels,
                                       margin_left_in_pixels);
   }
 
-  int new_content_width = page_size_in_pixels.width -
+  float new_content_width = page_size_in_pixels.width -
                           margin_left_in_pixels - margin_right_in_pixels;
-  int new_content_height = page_size_in_pixels.height -
+  float new_content_height = page_size_in_pixels.height -
                            margin_top_in_pixels - margin_bottom_in_pixels;
 
   // Invalid page size and/or margins. We just use the default setting.
   if (new_content_width < 1 || new_content_height < 1) {
     CHECK(frame != NULL);
     page_css_params = GetCssPrintParams(NULL, page_index, page_params);
     return page_css_params;
   }
 
+  page_css_params.page_size =
+      gfx::Size(ConvertUnit(page_size_in_pixels.width, kPixelsPerInch, dpi),
+                ConvertUnit(page_size_in_pixels.height, kPixelsPerInch, dpi));
   page_css_params.content_size =
       gfx::Size(ConvertUnit(new_content_width, kPixelsPerInch, dpi),
-                ConvertUnit(new_content_height, kPixelsPerInch, dpi));
-
-  if (original_page_size_in_pixels != page_size_in_pixels) {
-    page_css_params.page_size =
-        gfx::Size(ConvertUnit(page_size_in_pixels.width, kPixelsPerInch, dpi),
-                  ConvertUnit(page_size_in_pixels.height, kPixelsPerInch, dpi));
-  } else {
-    // Printing frame doesn't have any page size css. Pixels to dpi conversion
-    // causes rounding off errors. Therefore use the default page size values
-    // directly.
-    page_css_params.page_size = page_params.page_size;
-  }
+              ConvertUnit(new_content_height, kPixelsPerInch, dpi));
 
   page_css_params.margin_top =
       ConvertUnit(margin_top_in_pixels, kPixelsPerInch, dpi);
   page_css_params.margin_left =
       ConvertUnit(margin_left_in_pixels, kPixelsPerInch, dpi);
   return page_css_params;
 }
 
 double FitPrintParamsToPage(const PrintMsg_Print_Params& page_params,
                             PrintMsg_Print_Params* params_to_fit) {
@@ skipping 2060 matching lines @@
       blink::WebConsoleMessage::LevelWarning, message));
   return false;
 }
 
 void PrintWebViewHelper::ScriptingThrottler::Reset() {
   // Reset counter on successful print.
   count_ = 0;
 }
 
 }  // namespace printing