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

Source/core/dom/StyleElement.cpp

Index: Source/core/dom/StyleElement.cpp
diff --git a/Source/core/dom/StyleElement.cpp b/Source/core/dom/StyleElement.cpp
index cc7378d4983ffc4801bf41a850252f663b3b18fc..e875a9f159258b3e46f8745e3340bda4ce14c4ca 100644
--- a/Source/core/dom/StyleElement.cpp
+++ b/Source/core/dom/StyleElement.cpp
@@ -153,6 +153,10 @@ void StyleElement::createSheet(Element* e, const String& text)
     // 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