Print with the correct physical dimensions when specified

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 658 matching lines @@
     frame->printEnd();
   }
   ComputeWebKitPrintParamsInDesiredDpi(print_params, &web_print_params_);
 }
 
 PrepareFrameAndViewForPrint::~PrepareFrameAndViewForPrint() {
   FinishPrinting();
 }
 
 void PrepareFrameAndViewForPrint::ResizeForPrinting() {
   // Layout page according to printer page size. Since WebKit shrinks the

[eae, 2016/03/23 21:16:56]

This comment needs updating. Would also be great if you could include some of
the details from the bug and change list description here.

   // size of the page automatically (from 125% to 200%) we trick it to
   // think the page is 125% larger so the size of the page is correct for
   // minimum (default) scaling.
   // This is important for sites that try to fill the page.
-  // The 1.25 value is |printingMinimumShrinkFactor|.
+  // The 1.33 value is |printingMinimumShrinkFactor|.
   gfx::Size print_layout_size(web_print_params_.printContentArea.width,
                               web_print_params_.printContentArea.height);
   print_layout_size.set_height(
-      static_cast<int>(static_cast<double>(print_layout_size.height()) * 1.25));
+      static_cast<int>(static_cast<double>(print_layout_size.height()) * 1.33));

[eae, 2016/03/23 21:16:56]

How about making this a constant and using it both here and below? (and ideally
in blink, that might be hard though).

 
   if (!frame())
     return;
   blink::WebView* web_view = frame_.view();
   // Backup size and offset.
   if (blink::WebFrame* web_frame = web_view->mainFrame())
     prev_scroll_offset_ = web_frame->scrollOffset();
   prev_view_size_ = web_view->size();
 
   web_view->resize(print_layout_size);
@@ skipping 1079 matching lines @@
 
   MetafileSkiaWrapper::SetMetafileOnCanvas(*canvas, metafile);
 
 #if defined(ENABLE_PRINT_PREVIEW)
   if (params.params.display_header_footer) {
     // TODO(thestig): Figure out why Linux needs this. The value may be
     // |printingMinimumShrinkFactor|.
 #if defined(OS_WIN)
     const float fudge_factor = 1;
 #else
-    const float fudge_factor = 1.25;
+    const float fudge_factor = 1.33;
 #endif
     // |page_number| is 0-based, so 1 is added.
     PrintHeaderAndFooter(canvas, params.page_number + 1,
                          print_preview_context_.total_page_count(), *frame,
                          scale_factor / fudge_factor, page_layout_in_points,
                          params.params);
   }
 #endif  // defined(ENABLE_PRINT_PREVIEW)
 
   float webkit_scale_factor =
@@ skipping 439 matching lines @@
       blink::WebConsoleMessage::LevelWarning, message));
   return false;
 }
 
 void PrintWebViewHelper::ScriptingThrottler::Reset() {
   // Reset counter on successful print.
   count_ = 0;
 }
 
 }  // namespace printing