Don't let rounding prematurely influence document size when printing

third_party/WebKit/Source/core/dom/Document.cpp

Index: third_party/WebKit/Source/core/dom/Document.cpp
diff --git a/third_party/WebKit/Source/core/dom/Document.cpp b/third_party/WebKit/Source/core/dom/Document.cpp
index 179c42293ac068b106321168aaac0d7ce5566771..8d9182d5f42d7311877d1e103fb516a397394af8 100644
--- a/third_party/WebKit/Source/core/dom/Document.cpp
+++ b/third_party/WebKit/Source/core/dom/Document.cpp
@@ -1991,12 +1991,12 @@ bool Document::isPageBoxVisible(int pageIndex)
     return styleForPage(pageIndex)->visibility() != HIDDEN; // display property doesn't apply to @page.
 }
 
-void Document::pageSizeAndMarginsInPixels(int pageIndex, IntSize& pageSize, int& marginTop, int& marginRight, int& marginBottom, int& marginLeft)
+void Document::pageSizeAndMarginsInPixels(int pageIndex, FloatSize& pageSize, int& marginTop, int& marginRight, int& marginBottom, int& marginLeft)
 {
     RefPtr<ComputedStyle> style = styleForPage(pageIndex);
 
-    int width = pageSize.width();
-    int height = pageSize.height();
+    float width = pageSize.width();

[eae, 2016/07/12 22:26:39]

This does not look right. Pages are always in full pixels. Even if that hadn't
been the case we should not use floats for sizes in layout. That's what
LayoutUnit is for.

[rhogan, 2016/07/13 18:27:13]

The main user of this API is print_web_view_helper.cc, and it does need to
consume the un-snapped value so that it can scale it without losing accuracy.
Maybe I should rename the method to pageSizeAndMarginsInSubpixels?

[eae, 2016/07/13 20:42:26]

In that case we need to use either LayoutUnits or doubles. Floats are not
precise enough.

+    float height = pageSize.height();
     switch (style->getPageSizeType()) {
     case PAGE_SIZE_AUTO:
         break;
@@ -2017,7 +2017,7 @@ void Document::pageSizeAndMarginsInPixels(int pageIndex, IntSize& pageSize, int&
     default:
         ASSERT_NOT_REACHED();
     }
-    pageSize = IntSize(width, height);
+    pageSize = FloatSize(width, height);
 
     // The percentage is calculated with respect to the width even for margin top and bottom.
     // http://www.w3.org/TR/CSS2/box.html#margin-properties