geckodriver: Adds TakesElementScreenshot

This is already available in Marionette. This allows us to call Marionette
from Selenium to take screenshots of elements.

Source-Repo: https://github.com/mozilla/geckodriver
Source-Revision: cb67c0aa66e3d50223de8e79eb4e1333bfb09401

committer: jgraham <james@hoppipolla.co.uk>

--HG--
extra : rebase_source : b73deed5b7ea1b4de94a402453b5427f96510204

testing/geckodriver/src/marionette.rs

@@ -33,8 +33,8 @@ use webdriver::command::WebDriverCommand::{
     ElementClick, ElementTap, ElementClear, ElementSendKeys,
     ExecuteScript, ExecuteAsyncScript, GetCookies, GetCookie, AddCookie,
     DeleteCookies, DeleteCookie, SetTimeouts, DismissAlert,
-    AcceptAlert, GetAlertText, SendAlertText, TakeScreenshot, Extension,
+    AcceptAlert, GetAlertText, SendAlertText, TakeScreenshot, TakeElementScreenshot,
-    SetWindowPosition, GetWindowPosition};
+    Extension, SetWindowPosition, GetWindowPosition};
 use webdriver::command::{
     NewSessionParameters, GetParameters, WindowSizeParameters, SwitchToWindowParameters,
     SwitchToFrameParameters, LocatorParameters, JavascriptCommandParameters,
@@ -568,7 +568,7 @@ impl MarionetteSession {
             IsSelected(_) | GetElementAttribute(_, _) | GetElementProperty(_, _) |
             GetCSSValue(_, _) | GetElementText(_) |
             GetElementTagName(_) | IsEnabled(_) | ExecuteScript(_) | ExecuteAsyncScript(_) |
-            GetAlertText | TakeScreenshot => {
+            GetAlertText | TakeScreenshot | TakeElementScreenshot(_) => {
                 let value = try_opt!(resp.result.find("value"),
                                      ErrorStatus::UnknownError,
                                      "Failed to find value field");
@@ -934,6 +934,13 @@ impl MarionetteCommand {
                 data.insert("full".to_string(), Json::Boolean(false));
                 (Some("takeScreenshot"), Some(Ok(data)))
             },
+            TakeElementScreenshot(ref e) => {
+                let mut data = BTreeMap::new();
+                data.insert("id".to_string(), e.id.to_json());
+                data.insert("highlights".to_string(), Json::Array(vec![]));
+                data.insert("full".to_string(), Json::Boolean(false));
+                (Some("takeScreenshot"), Some(Ok(data)))
+            },
             Extension(ref extension) => {
                 match extension {
                     &GeckoExtensionCommand::GetContext => (Some("getContext"), None),