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

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 9d3ef2b37aa6d94de92edf79cf46ab0b0f2843c1..bbd83a7e8ec8b3951478826c5fc23855c280d2dd 100644
--- a/Source/core/html/shadow/PluginPlaceholderElement.js
+++ b/Source/core/html/shadow/PluginPlaceholderElement.js
@@ -6,16 +6,10 @@
 
 installClass('PluginPlaceholderElement', function(PluginPlaceholderElementPrototype) {
     PluginPlaceholderElementPrototype.createdCallback = function() {
-        // FIXME: Move style out of script and into CSS.
-
         this.id = 'plugin-placeholder';
-        this.style.width = '100%';
-        this.style.height = '100%';
-        this.style.overflow = 'hidden';
-        this.style.display = 'flex';
-        this.style.alignItems = 'center';
-        this.style.backgroundColor = 'gray';
-        this.style.font = '12px -webkit-control';
+
+        var styleElement = document.createElement('style');
+        styleElement.textContent = loadPlatformResource('PluginPlaceholderElement.css');

[haraken, 2014/10/04 00:56:20]

Just to confirm: loadPlatformResource takes a relative path, right?

[jbroman, 2014/10/04 03:36:06]

At the moment, it passes the path to Platform::loadResource, which is mapped to
data via a map in content::BlinkPlatformImpl (from a name to a resource ID), and
in blink_resources.grd (from a resource ID to a source filename).

The existing convention for resource names is filenames without any leading
path, which is why this does not need qualification.

(Unless vivekg's effort to refactor this mapping lands, this patch will be
broken into three to include the Chromium-side patch. But two of those will be
trivial. The Chromium side will look roughly like
https://codereview.chromium.org/556793006/, but with CSS instead of JS.)

 
         var contentElement = document.createElement('div');
         contentElement.id = 'plugin-placeholder-content';
@@ -26,6 +20,7 @@ installClass('PluginPlaceholderElement', function(PluginPlaceholderElementProtot
         messageElement.id = 'plugin-placeholder-message';
 
         contentElement.appendChild(messageElement);
+        this.appendChild(styleElement);
         this.appendChild(contentElement);
 
         this.messageElement = messageElement;