[DevTools] Update media queries when resizing with emulation on.

Source/web/WebViewImpl.cpp

 /*
  * Copyright (C) 2011, 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 1601 matching lines @@
         updatePageDefinedViewportConstraints(mainFrameImpl()->frame()->document()->viewportDescription());
         updateMainFrameLayoutSize();
 
         // If the virtual viewport pinch mode is enabled, the main frame will be resized
         // after layout so it can be sized to the contentsSize.
         if (!pinchVirtualViewportEnabled() && mainFrameImpl()->frameView())
             mainFrameImpl()->frameView()->resize(m_size);
 
         if (pinchVirtualViewportEnabled())
             page()->frameHost().pinchViewport().setSize(m_size);
+
+        // When device emulation is enabled, device size values may change - they are
+        // usually set equal to the view size. These values are not considered viewport-dependent
+        // (see MediaQueryExp::isViewportDependent), since they are only viewport-dependent in emulation mode,
+        // and thus will not be invalidated in |FrameView::performPreLayoutTasks|.
+        // Therefore we should force explicit media queries invalidation here.
+        if (page()->inspectorController().deviceEmulationEnabled()) {
+            if (Document* document = mainFrameImpl()->frame()->document())
+                document->mediaQueryAffectingValueChanged();
+        }
     }
 
     if (settings()->viewportEnabled() && !m_fixedLayoutSizeLock) {
         // Relayout immediately to recalculate the minimum scale limit.
         if (view->needsLayout())
             view->layout();
 
         if (shouldAnchorAndRescaleViewport) {
             float viewportWidthRatio = static_cast<float>(newSize.width) / oldSize.width;
             float contentsWidthRatio = static_cast<float>(contentsSize().width()) / oldContentsWidth;
@@ skipping 2511 matching lines @@
     const PageScaleConstraints& constraints = m_pageScaleConstraintsSet.pageDefinedConstraints();
 
     if (!mainFrameImpl() || !mainFrameImpl()->frameView())
         return false;
 
     return mainFrameImpl()->frameView()->layoutSize().width() == m_size.width
         || (constraints.minimumScale == constraints.maximumScale && constraints.minimumScale != -1);
 }
 
 } // namespace blink