Add a custom element to own structure of shadow DOM plugin placeholders.

Source/core/html/shadow/PluginPlaceholderElement.cpp

Index: Source/core/html/shadow/PluginPlaceholderElement.cpp
diff --git a/Source/core/html/shadow/PluginPlaceholderElement.cpp b/Source/core/html/shadow/PluginPlaceholderElement.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..aeb6d7b90f3b5865b394ccc1d1fa918a34475c08
--- /dev/null
+++ b/Source/core/html/shadow/PluginPlaceholderElement.cpp
@@ -0,0 +1,87 @@
+// 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/ExceptionState.h"
+#include "core/CSSPropertyNames.h"
+#include "core/CSSValueKeywords.h"
+#include "wtf/StdLibExtras.h"
+#include "wtf/text/AtomicString.h"
+
+namespace blink {
+
+PluginPlaceholderElement::PluginPlaceholderElement(Document& document)
+    : HTMLDivElement(document)
+{
+}
+
+PassRefPtrWillBeRawPtr<PluginPlaceholderElement> PluginPlaceholderElement::create(Document& document)
+{
+    RefPtrWillBeRawPtr<PluginPlaceholderElement> element = adoptRefWillBeNoop(new PluginPlaceholderElement(document));
+
+    if (element->initializePlaceholderElements())

[esprehn, 2014/08/29 21:13:26]

This shouldn't be allowed to return nullptr, create() should never fail.

Also this should use Shadow DOM, you want to do ensureUserAgentShadowRoot()
here.

[jbroman, 2014/08/30 13:55:48]

The shadow root host is the HTMLPlugInElement (object, embed or applet). This
element is intended to be attached as a child of that shadow root, so it doesn't
itself need a UA shadow root.

While it could implicitly attach itself to the shadow root of an
HTMLPlugInElement it took as a construction argument, that behaviour does not
seem expected.

See the new Internals::forcePluginPlaceholder overload for an example; the
production call site will probably be in the Source/web/ glue class
(WebPluginPlaceholderContainerImpl, or whatever other monstrous name it ends up
getting).

+        return element.release();
+
+    return nullptr;
+}
+
+void PluginPlaceholderElement::trace(Visitor* visitor)
+{
+    visitor->trace(m_messageElement);
+    HTMLDivElement::trace(visitor);
+}
+
+void PluginPlaceholderElement::setMessage(const String& message)
+{
+    m_messageElement->setInnerHTML(message, ASSERT_NO_EXCEPTION);
+}
+
+bool PluginPlaceholderElement::initializePlaceholderElements()

[esprehn, 2014/08/29 21:13:26]

Just use didAddUserAgentShadowRoot(ShadowRoot& root)

and append these elements to the shadow root.

[jbroman, 2014/08/30 13:55:48]

See above.

+{
+    // Produces DOM roughly equivalent to the following HTML:
+    //
+    // <div id="plugin-placeholder">
+    //   <div id="plugin-placeholder-content">
+    //     <div id="plugin-placeholder-message"></div>
+    //   </div>
+    // </div>
+
+    // FIXME: Move style out of C++ and into CSS.
+
+    TrackExceptionState exceptionState;
+
+    DEFINE_STATIC_LOCAL(AtomicString, id, ("plugin-placeholder"));
+    setIdAttribute(id);
+    setInlineStyleProperty(CSSPropertyWidth, 100, CSSPrimitiveValue::CSS_PERCENTAGE);
+    setInlineStyleProperty(CSSPropertyHeight, 100, CSSPrimitiveValue::CSS_PERCENTAGE);
+    setInlineStyleProperty(CSSPropertyOverflow, CSSValueHidden);
+    setInlineStyleProperty(CSSPropertyDisplay, CSSValueFlex);
+    setInlineStyleProperty(CSSPropertyAlignItems, CSSValueCenter);
+    setInlineStyleProperty(CSSPropertyBackgroundColor, CSSValueGray);
+    setInlineStyleProperty(CSSPropertyFont, "12px -webkit-control");
+
+    DEFINE_STATIC_LOCAL(AtomicString, contentId, ("plugin-placeholder-content"));
+    RefPtrWillBeRawPtr<HTMLDivElement> contentElement = HTMLDivElement::create(document());
+    contentElement->setIdAttribute(contentId);
+    contentElement->setInlineStyleProperty(CSSPropertyTextAlign, CSSValueCenter);
+    contentElement->setInlineStyleProperty(CSSPropertyMargin, CSSValueAuto);
+
+    DEFINE_STATIC_LOCAL(AtomicString, messageId, ("plugin-placeholder-message"));
+    RefPtrWillBeRawPtr<HTMLDivElement> messageElement = HTMLDivElement::create(document());
+    messageElement->setIdAttribute(messageId);
+    m_messageElement = messageElement.get();
+    contentElement->appendChild(messageElement.release(), exceptionState);
+    if (exceptionState.hadException())

[esprehn, 2014/08/29 21:13:26]

ASSERT_NO_EXCEPTION

[jbroman, 2014/08/30 13:55:48]

Okay. I assumed that tracking the exception and possibly returning null was
preferred in this pattern, as that is what, for example, MediaControls::create
does.

If I rewrite this with Blink-in-JS, this point will be moot anyhow.

+        return false;
+
+    appendChild(contentElement.release(), exceptionState);

[esprehn, 2014/08/29 21:13:26]

ASSERT_NO_EXCEPTION, don't check it. Internal code should never throw.

[jbroman, 2014/08/30 13:55:48]

Ditto.

+    if (exceptionState.hadException())
+        return false;
+
+    return true;

[esprehn, 2014/08/29 21:13:26]

no return value, just use the Shadow DOM framework.

[jbroman, 2014/08/30 13:55:48]

I understand the "no return value", though I'm not sure what you mean by "use
the Shadow DOM frameowrk".

+}
+
+} // namespace blink