Initial containing block for print not affected by page zoom.

third_party/WebKit/Source/core/css/MediaValues.cpp

 // Copyright 2014 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 "core/css/MediaValues.h"
 
 #include "core/css/CSSHelper.h"
 #include "core/css/MediaValuesCached.h"
 #include "core/css/MediaValuesDynamic.h"
 #include "core/dom/Document.h"
@@ skipping 14 matching lines @@
 namespace blink {
 
 MediaValues* MediaValues::createDynamicIfFrameExists(LocalFrame* frame) {
   if (frame)
     return MediaValuesDynamic::create(frame);
   return MediaValuesCached::create();
 }
 
 double MediaValues::calculateViewportWidth(LocalFrame* frame) {
   ASSERT(frame && frame->view() && frame->document());
-  int viewportWidth = frame->view()->layoutSize(IncludeScrollbars).width();
-  return adjustDoubleForAbsoluteZoom(
-      viewportWidth, frame->document()->layoutViewItem().styleRef());
+  return frame->view()->viewportSizeForViewportUnits().width();
 }
 
 double MediaValues::calculateViewportHeight(LocalFrame* frame) {
   ASSERT(frame && frame->view() && frame->document());
-  int viewportHeight = frame->view()->layoutSize(IncludeScrollbars).height();
-  return adjustDoubleForAbsoluteZoom(
-      viewportHeight, frame->document()->layoutViewItem().styleRef());
+  return frame->view()->viewportSizeForViewportUnits().height();

[bokan, 2017/03/09 16:29:56]

I think this is slightly wrong. The reason we have a specific viewportSize for
ViewportUnits is because 100vh is actually taller than the ICB by the height of
the URL bar and I think Media Queries should really report the ICB. I would
either add a zoomedLayoutSize method on FrameView or keep the zoom logic in
here.

[rune, 2017/03/09 17:47:36]

Why is there a difference between ICB and viewport units? The documentation says
it's in order to match Safari. Is that the only reason? 100% height relative to
the ICB is different from 100vh in Chromium, which is strange:

http://jsbin.com/bepejugowu/1/edit?html,css,js,output

Based on that jsbin snippet vh is relative to the whole screen while the ICB is
relative to the available space without the URL-bar. I noticed that layout ng is
actually using viewportSizeForViewportUnits for its constraint space. That would
be different from the current code afaict?

[rune, 2017/03/09 22:04:55]

I added a new viewportSizeForMediaQueries() instead.

 }
 
 int MediaValues::calculateDeviceWidth(LocalFrame* frame) {
   DCHECK(frame && frame->view() && frame->settings() && frame->page());
   blink::WebScreenInfo screenInfo = frame->page()->chromeClient().screenInfo();
   int deviceWidth = screenInfo.rect.width;
   if (frame->settings()->getReportScreenSizeInPhysicalPixelsQuirk())
     deviceWidth = lroundf(deviceWidth * screenInfo.deviceScaleFactor);
   return deviceWidth;
 }
@@ skipping 161 matching lines @@
 
 LocalFrame* MediaValues::frameFrom(Document& document) {
   Document* executingDocument = document.importsController()
                                     ? document.importsController()->master()
                                     : &document;
   ASSERT(executingDocument);
   return executingDocument->frame();
 }
 
 }  // namespace blink