Implement window management devtools commands for headless.

headless/lib/headless_browser_browsertest.cc

Index: headless/lib/headless_browser_browsertest.cc
diff --git a/headless/lib/headless_browser_browsertest.cc b/headless/lib/headless_browser_browsertest.cc
index 9df187e8584ca4afed04957522cbdbc72afde87e..493b2c8c18eb94dc1f1baecd3b3ad3dc20ed7067 100644
--- a/headless/lib/headless_browser_browsertest.cc
+++ b/headless/lib/headless_browser_browsertest.cc
@@ -384,8 +384,8 @@ IN_PROC_BROWSER_TEST_F(HeadlessBrowserTest, DefaultSizes) {
 #if !defined(OS_MACOSX)
   // On Mac headless does not override the screen dimensions, so they are
   // left with the actual screen values.
-  EXPECT_EQ(kDefaultOptions.window_size.width(), screen_width);
-  EXPECT_EQ(kDefaultOptions.window_size.height(), screen_height);
+  EXPECT_EQ(kDefaultOptions.screen_size.width(), screen_width);
+  EXPECT_EQ(kDefaultOptions.screen_size.height(), screen_height);
 #endif  // !defined(OS_MACOSX)
   EXPECT_EQ(kDefaultOptions.window_size.width(), window_width);
   EXPECT_EQ(kDefaultOptions.window_size.height(), window_height);