Consider Zoom factor when getting bounding rect.

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

 /*
  * Copyright (C) 2005, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 95 matching lines @@
         [string setAttributes:attrs range:NSMakeRange(position, numCharacters)];
         position += numCharacters;
     }
     return [string autorelease];
 }
 
 WebPoint getBaselinePoint(FrameView* frameView, const EphemeralRange& range, NSAttributedString* string)
 {
     // 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());
+    float scale = frameView->frame().pageZoomFactor() * frameView->frame().textZoomFactor();

[yosin_UTC9, 2016/01/26 03:44:17]

Which coordinate space do you want to get?
See http://www.chromium.org/developers/design-documents/blink-coordinate-spaces

We may want to use coodinate space conversion function |FrameView|.

[Shu Chen, 2016/01/26 13:06:43]

Done. Will the new change work?

+    FloatRect rect = createRange(range)->boundingRect();
+    rect.setX(rect.x() * scale);
+    rect.setY(rect.y() * scale);
+    rect.setWidth(rect.width() * scale);
+    rect.setHeight(rect.height() * scale);
+    IntRect stringRect = enclosingIntRect(rect);
     IntPoint stringPoint = stringRect.minXMaxYCorner();
     stringPoint.setY(frameView->height() - stringPoint.y());
 
     // Adjust for the font's descender. AppKit wants the baseline point.
     if ([string length]) {
         NSDictionary* attributes = [string attributesAtIndex:0 effectiveRange:NULL];
         if (NSFont* font = [attributes objectForKey:NSFontAttributeName])
             stringPoint.move(0, ceil(-[font descender]));
     }
     return stringPoint;
@@ skipping 40 matching lines @@
     if (ephemeralRange.isNull())
         return nil;
 
     NSAttributedString* result = attributedSubstringFromRange(ephemeralRange);
     if (baselinePoint)
         *baselinePoint = getBaselinePoint(frame->view(), ephemeralRange, result);
     return result;
 }
 
 } // namespace blink