Implement FullScreen using top layer.

Source/core/css/resolver/StyleAdjuster.cpp

Index: Source/core/css/resolver/StyleAdjuster.cpp
diff --git a/Source/core/css/resolver/StyleAdjuster.cpp b/Source/core/css/resolver/StyleAdjuster.cpp
index cffe90e1a6a699f5bde5aa09d48f237edde15443..3adb76cc96f55837bee250e90ee6f3cca2c26b89 100644
--- a/Source/core/css/resolver/StyleAdjuster.cpp
+++ b/Source/core/css/resolver/StyleAdjuster.cpp
@@ -34,6 +34,8 @@
 #include "core/dom/ContainerNode.h"
 #include "core/dom/Document.h"
 #include "core/dom/Element.h"
+#include "core/dom/Fullscreen.h"
+#include "core/frame/FrameHost.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/Settings.h"
 #include "core/frame/UseCounter.h"
@@ -44,6 +46,7 @@
 #include "core/html/HTMLTextAreaElement.h"
 #include "core/layout/LayoutReplaced.h"
 #include "core/layout/LayoutTheme.h"
+#include "core/page/Page.h"
 #include "core/style/ComputedStyle.h"
 #include "core/style/ComputedStyleConstants.h"
 #include "core/svg/SVGSVGElement.h"
@@ -177,6 +180,18 @@ void StyleAdjuster::adjustComputedStyle(ComputedStyle& style, const ComputedStyl
         adjustStyleForFirstLetter(style);
 
         adjustStyleForDisplay(style, parentStyle, e ? &e->document() : 0);
+
+        if (e) {
+            if (Fullscreen::isActiveFullScreenElement(*e)) {
+                // We need to size the fullscreen element to the inner viewport and not to the
+                // outer viewport (what percentage would do). Unfortunately CSS can't handle
+                // that as we don't expose this information. FIXME: We should find a way to
+                // get this standardized.
+                IntSize viewportSize = e->document().page()->frameHost().visualViewport().size();
+                style.setWidth(Length(viewportSize.width(), Fixed));
+                style.setHeight(Length(viewportSize.height(), Fixed));
+            }
+        }
     } else {
         adjustStyleForFirstLetter(style);
     }