Compute the popup location/size correctly when use-zoom-for-dsf is enabled.

third_party/WebKit/public/web/WebWidgetClient.h

Index: third_party/WebKit/public/web/WebWidgetClient.h
diff --git a/third_party/WebKit/public/web/WebWidgetClient.h b/third_party/WebKit/public/web/WebWidgetClient.h
index 41fe6692ea5aac06cdf84e4e3614cece960bdede..1eeff1bd3844f09c520c16ab8411fec90fbb5283 100644
--- a/third_party/WebKit/public/web/WebWidgetClient.h
+++ b/third_party/WebKit/public/web/WebWidgetClient.h
@@ -175,6 +175,15 @@ public:
     // press or gesture tap.
     // Note: This is called even when the mouse down event is prevent default.
     virtual void onMouseDown(const WebNode& mouseDownNode) { }
+
+    // Converts the |rect| from Blink's Viewport coordinates to the
+    // coordinates in the native window used to display the content, in
+    // DIP.  They're identical in tradional world, but will differ when
+    // use-zoom-for-dsf feature is eanbled, and Viewport coordinates
+    // becomes DSF times larger than window coordinates.
+    // TODO(oshima): Update this comment when all platforms are migrated.
+    virtual void convertViewportToWindow(WebRect* rect) {}
+
 protected:
     ~WebWidgetClient() { }
 };