DevTools: [MediaQueryInspector] Compute media query length on backend

Source/core/inspector/InspectorCSSAgent.cpp

Index: Source/core/inspector/InspectorCSSAgent.cpp
diff --git a/Source/core/inspector/InspectorCSSAgent.cpp b/Source/core/inspector/InspectorCSSAgent.cpp
index c54fe65b658c9cd8bc39f031025f3208366027f9..df588c15cc54c3c503239b64fd1f2ee0aa8c505a 100644
--- a/Source/core/inspector/InspectorCSSAgent.cpp
+++ b/Source/core/inspector/InspectorCSSAgent.cpp
@@ -41,6 +41,7 @@
 #include "core/css/CSSStyleSheet.h"
 #include "core/css/MediaList.h"
 #include "core/css/MediaQuery.h"
+#include "core/css/MediaValues.h"
 #include "core/css/StylePropertySet.h"
 #include "core/css/StyleRule.h"
 #include "core/css/StyleSheet.h"
@@ -1024,6 +1025,11 @@ PassRefPtr<TypeBuilder::CSS::CSSMedia> InspectorCSSAgent::buildMediaObject(const
                 .setValue(expValue.value)
                 .setUnit(String(valueName))
                 .setFeature(mediaQueryExp->mediaFeature());
+            RefPtr<MediaValues> mediaValues = MediaValues::createDynamicIfFrameExists(parentStyleSheet->ownerDocument()->frame());
+            int computedLength;
+            if (mediaValues->computeLength(expValue.value, expValue.unit, computedLength))
+                mediaQueryExpression->setComputedLength(computedLength);
+
             expressionArray->addItem(mediaQueryExpression);
             hasExpressionItems = true;
         }