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

public/blink_resources.grd

Index: public/blink_resources.grd
diff --git a/public/blink_resources.grd b/public/blink_resources.grd
index 40c0d54d20063a136ef72c4d1cff5451c3556b1f..ed4f1a2027807f9f1c3112c9d85eda9cb2ee1254 100644
--- a/public/blink_resources.grd
+++ b/public/blink_resources.grd
@@ -50,6 +50,7 @@
       <include name="IDR_SUGGESTION_PICKER_JS" file="../Source/web/resources/suggestionPicker.js" type="BINDATA"/>
       <include name="IDR_COLOR_SUGGESTION_PICKER_CSS" file="../Source/web/resources/colorSuggestionPicker.css" type="BINDATA"/>
       <include name="IDR_COLOR_SUGGESTION_PICKER_JS" file="../Source/web/resources/colorSuggestionPicker.js" type="BINDATA"/>
+      <include name="IDR_PLUGIN_PLACEHOLDER_ELEMENT_CSS" file="../Source/core/html/shadow/PluginPlaceholderElement.css" type="BINDATA"/>

[jbroman, 2014/09/02 15:44:04]

According to http://crbug.com/312586, this is the "not ready yet" approach (and
the various Python scripts to generated .h files are the deprecated way) to get
resources in Blink.

Unfortunately this approach requires a 3-sided change (as BlinkPlatformImpl
needs to know about new resources), and the build system does not seem to
correctly understand dependencies (I've needed to clobber it to see changes in
the .css file).

If that doesn't get better before this is ready to land, I'll probably move it
back to make-file-arrays.py instead.

       <if expr="pp_ifdef('use_concatenated_impulse_responses')">
         <include name="IDR_AUDIO_SPATIALIZATION_COMPOSITE" file="../Source/platform/audio/resources/Composite.wav" type="BINDATA"/>
       </if>