Don't pixel-snap overflow clips in clip paint property nodes.

third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp

 // Copyright 2015 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/paint/PaintPropertyTreeBuilderTest.h"
 
 #include "core/html/HTMLIFrameElement.h"
 #include "core/layout/LayoutTreeAsText.h"
 #include "core/paint/ObjectPaintProperties.h"
 #include "core/paint/PaintPropertyTreePrinter.h"
@@ skipping 3156 matching lines @@
   setBodyInnerHTML(
       "<div id='target' style='overflow: auto; width: 100px; height: 100px'>"
       "  <div style='width: 200px; height: 200px'></div>"
       "</div>");
 
   const ObjectPaintProperties* properties = paintPropertiesForElement("target");
   EXPECT_NE(CompositorElementId(),
             properties->scrollTranslation()->compositorElementId());
 }
 
+TEST_P(PaintPropertyTreeBuilderTest, OverflowClipSubpixelPosition) {
+  setBodyInnerHTML(
+      "<style>body { margin: 20px 30px; }</style>"
+      "<div id='clipper'"
+      "    style='position: relative; overflow: hidden; "
+      "           width: 400px; height: 300px; left: 1.5px'>"
+      "</div>");
+
+  LayoutBoxModelObject* clipper = toLayoutBoxModelObject(
+      document().getElementById("clipper")->layoutObject());
+  const ObjectPaintProperties* clipProperties = clipper->paintProperties();
+
+  EXPECT_EQ(LayoutPoint(FloatPoint(31.5, 20)), clipper->paintOffset());
+  EXPECT_EQ(FloatRect(31.5, 20, 400, 300),
+            clipProperties->overflowClip()->clipRect().rect());
+}
+
 }  // namespace blink