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

Source/core/html/shadow/PluginPlaceholderElement.cpp

 // Copyright 2014 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 "config.h"
 #include "core/html/shadow/PluginPlaceholderElement.h"
 
 #include "bindings/core/v8/V8PluginPlaceholderElement.h"
+#include "core/UserAgentStyleSheets.h"
 #include "core/dom/Document.h"
 #include "wtf/Assertions.h"
+#include "wtf/text/WTFString.h"
 
 namespace blink {
 
 PluginPlaceholderElement::PluginPlaceholderElement(Document& document)
     : HTMLDivElement(document)
 {
     ScriptWrappable::init(this);
 }
 
 PassRefPtrWillBeRawPtr<PluginPlaceholderElement> PluginPlaceholderElement::create(Document& document)
 {
     RefPtrWillBeRawPtr<PluginPlaceholderElement> element = adoptRefWillBeNoop(new PluginPlaceholderElement(document));
     bool success = V8PluginPlaceholderElement::PrivateScript::createCallbackMethod(document.frame(), element.get());
     ASSERT_UNUSED(success, success);
     return element.release();
 }
 
 void PluginPlaceholderElement::setMessage(const String& htmlMessage)
 {
     bool success = V8PluginPlaceholderElement::PrivateScript::messageAttributeSetter(document().frame(), this, htmlMessage);
     ASSERT_UNUSED(success, success);
 }
 
+String PluginPlaceholderElement::styleSource() const
+{
+    return pluginPlaceholderElementCss;

[abarth-chromium, 2014/09/02 22:34:34]

Please use GRD to load this resource.  See other callers of
Platform::current()->loadResource(...)

[jbroman, 2014/09/02 23:53:32]

I'd done that previously, though I had trouble. In particular, I wasn't able to
get it to actually rebuild when I changed a resource, unless I clobbered. I'll
try again, but I'm not sure if there's a trick here.

[jbroman, 2014/09/16 21:39:25]

Done.

+}
+
 v8::Handle<v8::Object> PluginPlaceholderElement::wrap(v8::Handle<v8::Object> creationContext, v8::Isolate* isolate)
 {
     return blink::wrap(this, creationContext, isolate);
 }
 
 } // namespace blink