Move creation of plugin placeholder DOM from JS to C++.

Source/core/html/shadow/PluginPlaceholderElement.js

Index: Source/core/html/shadow/PluginPlaceholderElement.js
diff --git a/Source/core/html/shadow/PluginPlaceholderElement.js b/Source/core/html/shadow/PluginPlaceholderElement.js
index 056cfbfa48dbffda4c31445ceb9594c6df849315..fe3581e379648b1d803c09767f02004e509adb05 100644
--- a/Source/core/html/shadow/PluginPlaceholderElement.js
+++ b/Source/core/html/shadow/PluginPlaceholderElement.js
@@ -5,54 +5,6 @@
 'use strict';
 
 installClass('PluginPlaceholderElement', function(PluginPlaceholderElementPrototype) {
-    // FIXME: Load this from a .css file.
-    var styleSource =
-        '#plugin-placeholder {' +
-        '    all: initial;' +
-        '    width: 100%;' +
-        '    height: 100%;' +
-        '    overflow: hidden;' +
-        '    display: flex;' +
-        '    align-items: center;' +
-        '    background: gray;' +
-        '    font: 12px -webkit-control;' +
-        '}' +
-        '#plugin-placeholder-content {' +
-        '    text-align: center;' +
-        '    margin: auto;' +
-        '}';
-
-    PluginPlaceholderElementPrototype.createdCallback = function() {
-        this.id = 'plugin-placeholder';
-
-        var styleElement = document.createElement('style');
-        styleElement.textContent = styleSource;
-
-        var contentElement = document.createElement('div');
-        contentElement.id = 'plugin-placeholder-content';
-
-        var messageElement = document.createElement('div');
-        messageElement.id = 'plugin-placeholder-message';
-
-        // FIXME: UI polish, l10n, etc. for the close button.
-        var closeButton = document.createElement('button');
-        closeButton.id = 'plugin-placeholder-close-button';
-        closeButton.textContent = 'Close';
-        closeButton.style.display = 'none';
-        closeButton.addEventListener('click', function() {
-            // FIXME: Record UMA Plugin_Hide_Click.
-            this.hide();
-        }.bind(this));
-
-        contentElement.appendChild(messageElement);
-        contentElement.appendChild(closeButton);
-        this.appendChild(styleElement);
-        this.appendChild(contentElement);
-
-        this.messageElement = messageElement;
-        this.closeButton = closeButton;
-    };
-
     PluginPlaceholderElementPrototype.hide = function() {
         var host = (this.parentNode instanceof ShadowRoot) ? this.parentNode.host : this;
         host.style.display = 'none';
@@ -90,14 +42,4 @@ installClass('PluginPlaceholderElement', function(PluginPlaceholderElementProtot
             }
         }
     };
-
-    Object.defineProperty(PluginPlaceholderElementPrototype, 'message', {
-        get: function() { return this.messageElement.textContent; },
-        set: function(message) { this.messageElement.textContent = message; },
-    });
-
-    Object.defineProperty(PluginPlaceholderElementPrototype, 'closeable', {
-        get: function() { return this.closeButton.style.display != 'none'; },
-        set: function(closeable) { this.closeButton.style.display = closeable ? '' : 'none'; },
-    });
 });