[DevTools] Use device metrics emulation implemented in content.

LayoutTests/inspector/styles/override-screen-size-expected.txt

Index: LayoutTests/inspector/styles/override-screen-size-expected.txt
diff --git a/LayoutTests/inspector/styles/override-screen-size-expected.txt b/LayoutTests/inspector/styles/override-screen-size-expected.txt
index bfd7f3eb8de8de4249fa246760897956eca60f51..ee4e04449452af31fc0c7dc50331dd97e68b8150 100644
--- a/LayoutTests/inspector/styles/override-screen-size-expected.txt
+++ b/LayoutTests/inspector/styles/override-screen-size-expected.txt
@@ -1,6 +1,7 @@
 Tests that screen dimension overrides affect media rules, body dimensions, and window.screen.
 
 Override: 480x800
+Page reloaded.
 Screen from page: 480x800
 Window from page: 480x800
 Body from page: 480x800
@@ -10,7 +11,7 @@ element.style  { ()
 
 [expanded] 
 media="screen" (override-screen-size.html)
-@media (max-device-height: 960px) and (max-device-width: 480px) (override-screen-size.html:9 -> override-screen-size.html:9:1)
+@media (max-device-height: 800px) and (max-device-width: 480px) (override-screen-size.html:9 -> override-screen-size.html:9:1)
 #main  { (override-screen-size.html:10 -> override-screen-size.html:10:5)
 background: green;
 
@@ -52,8 +53,5 @@ Current dimensions:
 Screen from page: 800x480
 Window from page: 800x480
 Body from page: 800x480
-Disable PageAgent:
-Screen size same as original - OK
-Enable PageAgent:
-Screen size same as original - OK
+Page reloaded.