DevTools: [MediaQueryInspector] Compute media query length on backend

LayoutTests/inspector-protocol/css/css-get-media-queries.html

Index: LayoutTests/inspector-protocol/css/css-get-media-queries.html
diff --git a/LayoutTests/inspector-protocol/css/css-get-media-queries.html b/LayoutTests/inspector-protocol/css/css-get-media-queries.html
index 4e4607a50e33182b92256139023b8261ae50fe0d..d65a5e086a9de2ece00bc286bf722dc95a2638ab 100644
--- a/LayoutTests/inspector-protocol/css/css-get-media-queries.html
+++ b/LayoutTests/inspector-protocol/css/css-get-media-queries.html
@@ -40,6 +40,8 @@ function test()
                     InspectorTest.log("        mediaExpression #" + k);
                     InspectorTest.log("            feature: " + expression.feature);
                     InspectorTest.log("            value: " + expression.value + expression.unit);
+                    if (expression.computedLength)
+                        InspectorTest.log("            computed length: " + expression.computedLength);
                 }
             }
         }