Don't bother layout until first navigation is done.

third_party/WebKit/Source/web/WebFrameContentDumper.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "public/web/WebFrameContentDumper.h"
 
 #include "core/editing/EphemeralRange.h"
 #include "core/editing/iterators/TextIterator.h"
 #include "core/editing/serializers/Serialization.h"
 #include "core/frame/LocalFrame.h"
@@ skipping 10 matching lines @@
 static void frameContentAsPlainText(size_t maxChars, LocalFrame* frame, StringBuilder& output)
 {
     Document* document = frame->document();
     if (!document)
         return;
 
     if (!frame->view())
         return;
 
     // Select the document body.
-    if (document->body()) {
+    if (!document->needsLayoutTreeUpdate() && document->body()) {
         const EphemeralRange range = EphemeralRange::rangeOfContents(*document->body());
 
         // The text iterator will walk nodes giving us text. This is similar to
         // the plainText() function in core/editing/TextIterator.h, but we implement the maximum
         // size and also copy the results directly into a wstring, avoiding the
         // string conversion.
         for (TextIterator it(range.startPosition(), range.endPosition()); !it.atEnd(); it.advance()) {
             it.text().appendTextToStringBuilder(output, 0, maxChars - output.length());
             if (output.length() >= maxChars)
                 return; // Filled up the buffer.
         }
     }
 
     // The separator between frames when the frames are converted to plain text.
     const LChar frameSeparator[] = { '\n', '\n' };
     const size_t frameSeparatorLength = WTF_ARRAY_LENGTH(frameSeparator);
 
     // Recursively walk the children.
     const FrameTree& frameTree = frame->tree();
     for (Frame* curChild = frameTree.firstChild(); curChild; curChild = curChild->tree().nextSibling()) {
         if (!curChild->isLocalFrame())
             continue;
         LocalFrame* curLocalChild = toLocalFrame(curChild);
+
         // Ignore the text of non-visible frames.
         LayoutView* contentLayoutObject = curLocalChild->contentLayoutObject();
         LayoutPart* ownerLayoutObject = curLocalChild->ownerLayoutObject();
         if (!contentLayoutObject || !contentLayoutObject->size().width() || !contentLayoutObject->size().height()
             || (contentLayoutObject->location().x() + contentLayoutObject->size().width() <= 0) || (contentLayoutObject->location().y() + contentLayoutObject->size().height() <= 0)
             || (ownerLayoutObject && ownerLayoutObject->style() && ownerLayoutObject->style()->visibility() != VISIBLE)) {
             continue;
         }
 
         // Make sure the frame separator won't fill up the buffer, and give up if
@@ skipping 38 matching lines @@
 
     if (toShow & LayoutAsTextDebug)
         behavior |= LayoutAsTextShowCompositedLayers | LayoutAsTextShowAddresses | LayoutAsTextShowIDAndClass | LayoutAsTextShowLayerNesting;
 
     if (toShow & LayoutAsTextPrinting)
         behavior |= LayoutAsTextPrintingMode;
 
     return externalRepresentation(toWebLocalFrameImpl(frame)->frame(), behavior);
 }
 }