headless: Allow both WW,HH and WWxHH forms for specifying window size

headless/app/headless_shell.cc

Index: headless/app/headless_shell.cc
diff --git a/headless/app/headless_shell.cc b/headless/app/headless_shell.cc
index 530a7c5dc3498e2d3b19d99b12c8ce6da043d47a..42a331fb9fbe326ce760a71229ee363ad895ebde 100644
--- a/headless/app/headless_shell.cc
+++ b/headless/app/headless_shell.cc
@@ -45,7 +45,7 @@ const char kDefaultScreenshotFileName[] = "screenshot.png";
 
 bool ParseWindowSize(std::string window_size, gfx::Size* parsed_window_size) {
   int width, height = 0;
-  if (sscanf(window_size.c_str(), "%dx%d", &width, &height) >= 2 &&
+  if (sscanf(window_size.c_str(), "%d%*[x,]%d", &width, &height) >= 2 &&
       width >= 0 && height >= 0) {
     parsed_window_size->set_width(width);
     parsed_window_size->set_height(height);