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..bc9f8c65722e079de40460acdd3393d2a1bbe205 100644
--- a/chrome/test/webdriver/commands/response.h
+++ b/chrome/test/webdriver/commands/response.h
@@ -14,11 +14,18 @@
 namespace webdriver {
 
 // All errors in webdriver must use this macro in order to send back
-// a proper stack trace to the client
+// a proper stack trace to the client.
 #define SET_WEBDRIVER_ERROR(response, msg, err) \
   response->SetError(err, msg, __FILE__, __LINE__); \
   LOG(ERROR) << msg
 
+// Error which need to send back a screenshot should use this macro.
+// |png| needs to be a string which contains the raw binary data of
+// the PNG file.
+#define SET_WEBDRIVER_ERROR_WITH_SCREENSHOT(response, msg, err , png) \
+  response->SetError(err, msg, __FILE__, __LINE__, png); \
+  LOG(ERROR) << msg
+
 // 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:
@@ -46,6 +53,16 @@ class Response {
   void SetError(ErrorCode error, const std::string& message,
                 const std::string& file, int line);
 
+  // Configures this response to report an error. The |file| and |line|
+  // parameters, which identify where in the source the error occurred, can be
+  // set using the |SET_WEBDRIVER_ERROR_WITH_SCREENSHOT| macro above.  Includes
+  // a screen shot of the tab which caused the error.
+  void SetError(ErrorCode error,
+                const std::string& message,
+                const std::string& file,
+                int line,
+                const std::string& png);
+
   // Sets a JSON field in this response. The |key| may be a "." delimitted
   // string to indicate the value should be set in a nested object. Any
   // previously set value for the |key| will be deleted.