headless: make initial screen/window sizes configurable.

headless/public/headless_browser.cc

Index: headless/public/headless_browser.cc
diff --git a/headless/public/headless_browser.cc b/headless/public/headless_browser.cc
index bbc644b231cf9e37499e42661f8708a51aaa6cd8..994df72d2ae7a5f19af072371e532dd930ddb1f2 100644
--- a/headless/public/headless_browser.cc
+++ b/headless/public/headless_browser.cc
@@ -13,6 +13,7 @@ namespace headless {
 // Product name for building the default user agent string.
 namespace {
 const char kProductName[] = "HeadlessChrome";
+constexpr gfx::Size kDefaultWindowSize(800, 600);
 }
 
 Options::Options(int argc, const char** argv)
@@ -22,7 +23,8 @@ Options::Options(int argc, const char** argv)
       message_pump(nullptr),
       single_process_mode(false),
       disable_sandbox(false),
-      gl_implementation("osmesa") {}
+      gl_implementation("osmesa"),
+      window_size(kDefaultWindowSize) {}
 
 Options::Options(Options&& options) = default;
 
@@ -81,6 +83,11 @@ Builder& Builder::SetGLImplementation(const std::string& gl_implementation) {
   return *this;
 }
 
+Builder& Builder::SetWindowSize(const gfx::Size& window_size) {
+  options_.window_size = window_size;
+  return *this;
+}
+
 Options Builder::Build() {
   return std::move(options_);
 }