Remove frame flattening support as Chromium has no intention of using it

Source/core/rendering/TextAutosizer.cpp

Index: Source/core/rendering/TextAutosizer.cpp
diff --git a/Source/core/rendering/TextAutosizer.cpp b/Source/core/rendering/TextAutosizer.cpp
index fe3299faf9586233f3c56fb7635919e039d6b668..b50a44aa055d6fd3b111eccd4714bfb462a205e5 100644
--- a/Source/core/rendering/TextAutosizer.cpp
+++ b/Source/core/rendering/TextAutosizer.cpp
@@ -120,10 +120,8 @@ bool TextAutosizer::processSubtree(RenderObject* layoutRoot)
     // Largest area of block that can be visible at once (assuming the main
     // frame doesn't get scaled to less than overview scale), in CSS pixels.
     windowInfo.minLayoutSize = mainFrame->view()->layoutSize();
-    for (Frame* frame = m_document->frame(); frame; frame = frame->tree()->parent()) {
-        if (!frame->view()->isInChildFrameWithFrameFlattening())
-            windowInfo.minLayoutSize = windowInfo.minLayoutSize.shrunkTo(frame->view()->layoutSize());
-    }
+    for (Frame* frame = m_document->frame(); frame; frame = frame->tree()->parent())
+        windowInfo.minLayoutSize = windowInfo.minLayoutSize.shrunkTo(frame->view()->layoutSize());
 
     // The layoutRoot could be neither a container nor a cluster, so walk up the tree till we find each of these.
     RenderBlock* container = layoutRoot->isRenderBlock() ? toRenderBlock(layoutRoot) : layoutRoot->containingBlock();