Translate viewport related meta tags into @viewport descriptors as suggested by the CSS Device Adap…

Source/core/page/FrameView.cpp

Index: Source/core/page/FrameView.cpp
diff --git a/Source/core/page/FrameView.cpp b/Source/core/page/FrameView.cpp
index 26badff745b01edc786294db90f39d5761b6e9c3..2714c5f8a44080f4cc13d86befbb4c30bb3e7a7d 100644
--- a/Source/core/page/FrameView.cpp
+++ b/Source/core/page/FrameView.cpp
@@ -33,6 +33,7 @@
 #include "core/animation/DocumentTimeline.h"
 #include "core/css/FontLoader.h"
 #include "core/css/resolver/StyleResolver.h"
+#include "core/css/resolver/ViewportStyleResolver.h"
 #include "core/dom/DocumentMarkerController.h"
 #include "core/dom/OverflowEvent.h"
 #include "core/editing/FrameSelection.h"
@@ -2206,9 +2207,12 @@ void FrameView::performPostLayoutTasks()
     if (page)
         milestonesOfInterest = page->layoutMilestones();
 
+    bool viewportDidChange = false;
+
     if (m_nestedLayoutCount <= 1) {
         if (m_firstLayoutCallbackPending) {
             m_firstLayoutCallbackPending = false;
+            viewportDidChange = true;
             m_frame->loader()->didFirstLayout();
             if (milestonesOfInterest & DidFirstLayout)
                 milestonesAchieved |= DidFirstLayout;
@@ -2251,25 +2255,29 @@ void FrameView::performPostLayoutTasks()
 
     m_actionScheduler->resume();
 
-    // Viewport-dependent media queries may cause us to need completely different style information.
-    if (m_frame->document()->styleResolver()->affectedByViewportChange()) {
+    IntSize currentSize = layoutSize(IncludeScrollbars);
+    float currentZoomFactor = renderView->style()->zoom();
+
+    bool didResize = currentSize != m_lastViewportSize || currentZoomFactor != m_lastZoomFactor;
+    viewportDidChange |= didResize;
+
+    m_lastViewportSize = currentSize;
+    m_lastZoomFactor = currentZoomFactor;
+
+    // Viewport-dependent media queries and @viewport rue may cause us to need completely
+    // different style information.
+    if (viewportDidChange && m_frame->document()->styleResolver()->affectedByViewportChange()) {
+        m_frame->document()->styleResolver()->viewportStyleResolver()->resolve();
         m_frame->document()->styleResolverChanged(DeferRecalcStyle);
         InspectorInstrumentation::mediaQueryResultChanged(m_frame->document());
     }
 
     // Refetch render view since it can be destroyed by updateWidget() call above.
     renderView = this->renderView();
-    if (renderView && !renderView->printing()) {
-        IntSize currentSize = layoutSize(IncludeScrollbars);
-        float currentZoomFactor = renderView->style()->zoom();
-        bool resized = !m_firstLayout && (currentSize != m_lastViewportSize || currentZoomFactor != m_lastZoomFactor);
-        m_lastViewportSize = currentSize;
-        m_lastZoomFactor = currentZoomFactor;
-        if (resized) {
-            m_frame->eventHandler()->sendResizeEvent();
-            if (page && page->mainFrame() == m_frame)
-                InspectorInstrumentation::didResizeMainFrame(page);
-        }
+    if (renderView && !renderView->printing() && !m_firstLayout && didResize) {
+        m_frame->eventHandler()->sendResizeEvent();
+        if (page && page->mainFrame() == m_frame)
+            InspectorInstrumentation::didResizeMainFrame(page);
     }
 }