Tweaking IE driver obscured element algorithm

The algorithm used by the IE driver to detect obscured elements checks
the value of the pointer-events CSS computed style property. This
property can have valid values of "auto" and "none" which affect whether
to consider an element "obscured." However, the property can also
contain other values for SVG elements. If the element in question is not
an SVG element, then values other than "none" and "auto" must be
ignored, and the element considered not to obscure the target element.

cpp/iedriver/Element.cpp

@@ -376,6 +376,13 @@ bool Element::IsObscured(LocationInfo* click_location,
         break;
       }
 
+      bool is_list_element_svg = false;
+      CComPtr<ISVGElement> list_svg_element;
+      hr = element_in_list->QueryInterface<ISVGElement>(&list_svg_element);
+      if (SUCCEEDED(hr) && list_svg_element) {
+        is_list_element_svg = true;
+      }
+
       bool is_list_element_displayed;
       Element list_element_wrapper(element_in_list,
                                    this->containing_window_handle_);
@@ -407,7 +414,15 @@ bool Element::IsObscured(LocationInfo* click_location,
               // may be technically obscuring this element, but manipulating
               // it with the pointer device has no effect, so it is effectively
               // not obscuring this element.
-              is_obscured = true;
+              // It is possible for the pointer-events value to be set to
+              // values other than "none" or "auto" for SVG elements. Since
+              // we are currently throwing up our hands with SVG elements,
+              // if the value is anything other than "auto", assume the
+              // element is not obscured.
+              if (list_element_pointer_events_value == L"auto" &&
+                  !is_list_element_svg) {
+                is_obscured = true;
+              }
             }
           } else {
             // We were unable to retrieve the computed style, so we must assume