Revert 148647 "Remove frame flattening support as Chromium has n..."

trunk/Source/core/rendering/RenderIFrame.cpp

Index: trunk/Source/core/rendering/RenderIFrame.cpp
===================================================================
--- trunk/Source/core/rendering/RenderIFrame.cpp	(revision 148648)
+++ trunk/Source/core/rendering/RenderIFrame.cpp	(working copy)
@@ -37,9 +37,9 @@
 namespace WebCore {
 
 using namespace HTMLNames;
-
+    
 RenderIFrame::RenderIFrame(Element* element)
-    : RenderPart(element)
+    : RenderFrameBase(element)
 {
 }
 
@@ -57,7 +57,7 @@
 LayoutUnit RenderIFrame::minPreferredLogicalWidth() const
 {
     if (!isSeamless())
-        return RenderPart::minPreferredLogicalWidth();
+        return RenderFrameBase::minPreferredLogicalWidth();
 
     RenderView* childRoot = contentRootRenderer();
     if (!childRoot)
@@ -69,7 +69,7 @@
 LayoutUnit RenderIFrame::maxPreferredLogicalWidth() const
 {
     if (!isSeamless())
-        return RenderPart::maxPreferredLogicalWidth();
+        return RenderFrameBase::maxPreferredLogicalWidth();
 
     RenderView* childRoot = contentRootRenderer();
     if (!childRoot)
@@ -85,7 +85,7 @@
 
 bool RenderIFrame::requiresLayer() const
 {
-    return RenderPart::requiresLayer() || style()->resize() != RESIZE_NONE;
+    return RenderFrameBase::requiresLayer() || style()->resize() != RESIZE_NONE;
 }
 
 RenderView* RenderIFrame::contentRootRenderer() const
@@ -96,6 +96,35 @@
     return childFrameView ? childFrameView->frame()->contentRenderer() : 0;
 }
 
+bool RenderIFrame::flattenFrame() const
+{
+    if (!node() || !node()->hasTagName(iframeTag))
+        return false;
+
+    HTMLIFrameElement* element = static_cast<HTMLIFrameElement*>(node());
+    Frame* frame = element->document()->frame();
+
+    if (isSeamless())
+        return false; // Seamless iframes are already "flat", don't try to flatten them.
+
+    bool enabled = frame && frame->settings() && frame->settings()->frameFlatteningEnabled();
+
+    if (!enabled || !frame->page())
+        return false;
+
+    if (style()->width().isFixed() && style()->height().isFixed()) {
+        // Do not flatten iframes with scrolling="no".
+        if (element->scrollingMode() == ScrollbarAlwaysOff)
+            return false;
+        if (style()->width().value() <= 0 || style()->height().value() <= 0)
+            return false;
+    }
+
+    // Do not flatten offscreen inner frames during frame flattening, as flattening might make them visible.
+    IntRect boundingRect = absoluteBoundingBoxRectIgnoringTransforms();
+    return boundingRect.maxX() > 0 && boundingRect.maxY() > 0;
+}
+
 void RenderIFrame::layoutSeamlessly()
 {
     updateLogicalWidth();
@@ -133,6 +162,9 @@
         updateLogicalWidth();
         // No kids to layout as a replaced element.
         updateLogicalHeight();
+
+        if (flattenFrame())
+            layoutWithFlattening(style()->width().isFixed(), style()->height().isFixed());
     }
 
     m_overflow.clear();