[ChromeDriver] Handling iframe padding

When elements are inside iframe with padding, ChromeDriver didn't take
into account the padding while calculating element locations, and end up
getting wrong the wrong locations. Fixing by adding the padding value.

Bug: chromedriver:2259
Change-Id: If3b37a6f891636df7b22679ea91e00e31fa66a83
Reviewed-on: https://chromium-review.googlesource.com/1010886Reviewed-by: Jonathon Kereliuk <kereliuk@chromium.org>
Commit-Queue: John Chen <johnchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553150}

chrome/test/chromedriver/element_util.cc

@@ -230,8 +230,20 @@ Status GetElementBorder(
   base::StringToInt(border_top_str, &border_top_tmp);
   if (border_left_tmp == -1 || border_top_tmp == -1)
     return Status(kUnknownError, "failed to get border width of element");
-  *border_left = border_left_tmp;
-  *border_top = border_top_tmp;
+  std::string padding_left_str;
+  status = GetElementEffectiveStyle(frame, web_view, element_id, "padding-left",
+                                    &padding_left_str);
+  int padding_left = 0;
+  if (status.IsOk())
+    base::StringToInt(padding_left_str, &padding_left);
+  std::string padding_top_str;
+  status = GetElementEffectiveStyle(frame, web_view, element_id, "padding-top",
+                                    &padding_top_str);
+  int padding_top = 0;
+  if (status.IsOk())
+    base::StringToInt(padding_top_str, &padding_top);
+  *border_left = border_left_tmp + padding_left;
+  *border_top = border_top_tmp + padding_top;
   return Status(kOk);
 }