Consider Zoom factor when getting bounding rect.

third_party/WebKit/Source/web/mac/WebSubstringUtil.mm

Index: third_party/WebKit/Source/web/mac/WebSubstringUtil.mm
diff --git a/third_party/WebKit/Source/web/mac/WebSubstringUtil.mm b/third_party/WebKit/Source/web/mac/WebSubstringUtil.mm
index 350e9cb072ff92136e107450e6ab66a12decc15d..674e71488479330ed40b30c8a54f4980001edc0a 100644
--- a/third_party/WebKit/Source/web/mac/WebSubstringUtil.mm
+++ b/third_party/WebKit/Source/web/mac/WebSubstringUtil.mm
@@ -113,7 +113,7 @@ WebPoint getBaselinePoint(FrameView* frameView, const EphemeralRange& range, NSA
 {
     // Compute bottom left corner and convert to AppKit coordinates.
     // TODO(yosin) We shold avoid to create |Range| object. See crbug.com/529985.
-    IntRect stringRect = enclosingIntRect(createRange(range)->boundingRect());
+    IntRect stringRect = frameView->contentsToRootFrame(createRange(range)->boundingBox());

[keishi, 2016/01/29 05:49:14]

According to the comment boundingRect considers css transforms. Did you need to
change it to boundingBox?

[Shu Chen, 2016/01/29 05:57:59]

If using boundingRect, the result is wrong for zoom'ed page.

How can I verify wether boundingBox can work well with css transforms?

[yosin_UTC9, 2016/01/29 06:30:52]

Add CSS property "-webkit-transform", e.g. -webkit-transform: rotate(45deg)
https://developer.mozilla.org/en-US/docs/Web/CSS/transform

     IntPoint stringPoint = stringRect.minXMaxYCorner();
     stringPoint.setY(frameView->height() - stringPoint.y());