Move plugin placeholder style to CSS, and allow it to bypass main world CSP.

Source/core/dom/StyleElement.cpp

 /*
  * Copyright (C) 2006, 2007 Rob Buis
  * Copyright (C) 2008 Apple, Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 135 matching lines @@
     ASSERT(e);
     ASSERT(e->inDocument());
     Document& document = e->document();
     if (m_sheet)
         clearSheet(e);
 
     // Inline style added from an isolated world should bypass the main world's
     // CSP just as an inline script would.
     LocalFrame* frame = document.frame();
     bool shouldBypassMainWorldCSP = frame && frame->script().shouldBypassMainWorldCSP();
+    if (!shouldBypassMainWorldCSP && !m_whitelistedSource.isNull()) {
+        RELEASE_ASSERT(m_whitelistedSource == text);
+        shouldBypassMainWorldCSP = true;
+    }
 
     const ContentSecurityPolicy* csp = document.contentSecurityPolicy();
     bool passesContentSecurityPolicyChecks = shouldBypassMainWorldCSP
         || csp->allowStyleWithHash(text)
         || csp->allowStyleWithNonce(e->fastGetAttribute(HTMLNames::nonceAttr))
         || csp->allowInlineStyle(e->document().url(), m_startPosition.m_line);
 
     // If type is empty or CSS, this is a CSS style sheet.
     const AtomicString& type = this->type();
     if (isCSS(e, type) && passesContentSecurityPolicyChecks) {
@@ skipping 34 matching lines @@
 {
     document.styleEngine()->addPendingSheet();
 }
 
 void StyleElement::trace(Visitor* visitor)
 {
     visitor->trace(m_sheet);
 }
 
 }