Send screenshots back to the client for debugging

chrome/test/webdriver/commands/response.h

Index: chrome/test/webdriver/commands/response.h
diff --git a/chrome/test/webdriver/commands/response.h b/chrome/test/webdriver/commands/response.h
index b77404d2260d67f3cec7f43550806640770b6e7e..8486b1f82727a807cba511cea2dd6ce900bbb4e2 100644
--- a/chrome/test/webdriver/commands/response.h
+++ b/chrome/test/webdriver/commands/response.h
@@ -19,6 +19,16 @@ namespace webdriver {
   response->SetError(err, msg, __FILE__, __LINE__); \
   LOG(ERROR) << msg
 
+// Use this macro for errors in which a screenshot can be taken and
+// sent back to the client.  A proper stack trace will also be included.
+#define SET_WEBDRIVER_SCREENSHOT_ERROR(response, session, msg, err) { \
+  LOG(ERROR) << msg; \
+  std::string __screenshot__; \
+  session->ScreenshotAsBase64(&__screenshot__); \
+  response->SetError(err, msg, __FILE__, __LINE__); \
+  response->SetScreenshot(__screenshot__); \
+}
+
 // A simple class that encapsulates the information describing the response to
 // a |Command|. In Webdriver all responses must be sent back as a JSON value,
 // conforming to the spec found at:
@@ -52,11 +62,16 @@ class Response {
   // This object assumes ownership of |value|.
   void SetField(const std::string& key, Value* value);
 
+  // Sets the screenshot to return to the client for debugging.  The file must
+  // be a base64 encoded PNG file.
+  void SetScreenshot(const std::string& screenshot);
+
   // Returns this response as a JSON string.
   std::string ToJSON() const;
 
  private:
   DictionaryValue data_;
+  std::string screenshot_;
 
   DISALLOW_COPY_AND_ASSIGN(Response);
 };