Initial containing block for print not affected by page zoom.

third_party/WebKit/Source/core/frame/FrameView.h

Index: third_party/WebKit/Source/core/frame/FrameView.h
diff --git a/third_party/WebKit/Source/core/frame/FrameView.h b/third_party/WebKit/Source/core/frame/FrameView.h
index e02bffd3737469a2d86e41354e57a2b316ae6cdc..755b3b3365a6fdcd42d4de81e9494776d985e082 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.h
+++ b/third_party/WebKit/Source/core/frame/FrameView.h
@@ -760,8 +760,14 @@ class CORE_EXPORT FrameView final
   IntRect computeVisibleArea();
 
   // Viewport size that should be used for viewport units (i.e. 'vh'/'vw').
+  // May include the size of browser controls. See implementation for further
+  // documentation.
   FloatSize viewportSizeForViewportUnits() const;
 
+  // Initial containing block size for evaluating viewport-dependent media
+  // queries.
+  FloatSize viewportSizeForMediaQueries() const;
+
   ScrollAnchor* scrollAnchor() override { return &m_scrollAnchor; }
   void clearScrollAnchor();
   bool shouldPerformScrollAnchoring() const override;