Round visual rects when crossing frame boundaries.

third_party/WebKit/Source/core/layout/LayoutObjectTest.cpp

Index: third_party/WebKit/Source/core/layout/LayoutObjectTest.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutObjectTest.cpp b/third_party/WebKit/Source/core/layout/LayoutObjectTest.cpp
index 8a8ff1947d269a6290abedb8603d716de51fb17c..274ea86c5fd4c92f736ed487ddb929da28ab9330 100644
--- a/third_party/WebKit/Source/core/layout/LayoutObjectTest.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutObjectTest.cpp
@@ -181,4 +181,26 @@ TEST_F(LayoutObjectTest, LayoutViewMapToVisibleRectInAncestorSpace)
     EXPECT_EQ(rect, LayoutRect(4, 13, 0, 37));
 }
 
+TEST_F(LayoutObjectTest, LayoutViewMapToVisibleRectInAncestorSpaceSubpixelRounding)
+{
+    document().setBaseURLOverride(KURL(ParsedURLString, "http://test.com"));
+    setBodyInnerHTML(
+        "<style>body { margin: 0; }</style>"
+        "<div id=frameContainer style='position: relative; left: 0.5px'>"
+        "  <iframe id=frame style='position: relative; left: 0.5px' src='http://test.com' width='200' height='200' frameBorder='0'></iframe>"
+        "</div>");
+
+    Document& frameDocument = setupChildIframe(
+        "frame", "<style>body { margin: 0; }</style><div id='target' style='position: relative; width: 100px; height: 100px; left: 0.5px'>");
+    frameDocument.updateLayout();
+
+    LayoutBlock* frameContainer = toLayoutBlock(getLayoutObjectByElementId("frameContainer"));
+    LayoutObject* target = frameDocument.getElementById("target")->layoutObject();
+    LayoutRect rect(0, 0, 100, 100);
+    EXPECT_TRUE(target->mapToVisibleRectInAncestorSpace(frameContainer, rect));
+    // When passing from the iframe to the parent frame, the rect of (0.5, 0, 100, 100) is expanded to (0, 0, 100, 100), and then offset by
+    // the 0.5 offset of frameContainer.
+    EXPECT_EQ(LayoutRect(LayoutPoint(DoublePoint(0.5, 0)), LayoutSize(101, 100)), rect);
+}
+
 } // namespace blink