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 43e36433b062736fb3c28dc909f7e602b5672b3a..2efbb0f03a99d72a95516ecbb14a4ba7f358b987 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;