Send screenshots back to the client for debugging

chrome/test/webdriver/commands/response.cc

Index: chrome/test/webdriver/commands/response.cc
diff --git a/chrome/test/webdriver/commands/response.cc b/chrome/test/webdriver/commands/response.cc
index 920bad1d8dc55819d4bfae7782eb2d9b7d68ecd4..a869b1729d43734533d8b24d11507b55e6bad4b0 100644
--- a/chrome/test/webdriver/commands/response.cc
+++ b/chrome/test/webdriver/commands/response.cc
@@ -27,6 +27,7 @@ const char* const kStackTraceLineNumberKey = "stackTrace.lineNumber";
 Response::Response() {
   SetStatus(kSuccess);
   SetValue(Value::CreateNullValue());
+  screenshot_ = "";
 }
 
 Response::~Response() {}
@@ -60,6 +61,10 @@ void Response::SetError(ErrorCode error_code, const std::string& message,
   error->SetString(kStackTraceFileNameKey, file);
   error->SetInteger(kStackTraceLineNumberKey, line);
 
+  if (!screenshot_.empty()) {
+    error->SetString(kScreenKey, screenshot_);
+  }
+
   SetStatus(error_code);
   SetValue(error);
 }
@@ -68,6 +73,10 @@ void Response::SetField(const std::string& key, Value* value) {
   data_.Set(key, value);
 }
 
+void Response::SetScreenshot(const std::string& screenshot) {
+  screenshot_ = screenshot;
+}
+
 std::string Response::ToJSON() const {
   std::string json;
   base::JSONWriter::Write(&data_, false, &json);