Reset viewport to implicit when @viewport is removed.

Source/core/testing/Internals.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  * Copyright (C) 2013 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 962 matching lines @@
 {
     if (!document || !document->page()) {
         es.throwDOMException(InvalidAccessError);
         return String();
     }
     Page* page = document->page();
 
     // Update initial viewport size.
     IntSize initialViewportSize(availableWidth, availableHeight);
     document->page()->mainFrame()->view()->setFrameRect(IntRect(IntPoint::zero(), initialViewportSize));
-    document->styleResolver()->viewportStyleResolver()->resolve();
 
     ViewportArguments arguments = page->viewportArguments();
     PageScaleConstraints constraints = arguments.resolve(initialViewportSize, 980 /* defaultLayoutWidthForNonMobilePages */);
 
     constraints.fitToContentsWidth(constraints.layoutSize.width(), availableWidth);
 
     StringBuilder builder;
 
     builder.appendLiteral("viewport size ");
     builder.append(String::number(constraints.layoutSize.width()));
@@ skipping 1183 matching lines @@
         return false;
     sharedContext->getExtensions()->loseContextCHROMIUM(Extensions3D::GUILTY_CONTEXT_RESET_ARB, Extensions3D::INNOCENT_CONTEXT_RESET_ARB);
     // To prevent tests that call loseSharedGraphicsContext3D from being
     // flaky, we call finish so that the context is guaranteed to be lost
     // synchronously (i.e. before returning).
     sharedContext->finish();
     return true;
 }
 
 }