Plugin Power Saver: Implement pixel tests for plugin placeholders.

chrome/renderer/resources/plugins/plugin_poster.html

Index: chrome/renderer/resources/plugins/plugin_poster.html
diff --git a/chrome/renderer/resources/plugins/plugin_poster.html b/chrome/renderer/resources/plugins/plugin_poster.html
index e2d018d27c8b94aedf873e28fba4d622ae3313c1..962e9bcc7d7986fec461cae76fc7413a8223955f 100644
--- a/chrome/renderer/resources/plugins/plugin_poster.html
+++ b/chrome/renderer/resources/plugins/plugin_poster.html
@@ -91,6 +91,13 @@
       container.style.marginTop = marginTop;
       container.style.width = width;
       container.style.height = height;
+
+      if (plugin.didFinishIconRepositionForTesting) {
+        // Defer until reflow complete.
+        window.setTimeout(function() {
+          plugin.didFinishIconRepositionForTesting();
+        });
+      }
     };
   </script>
 </body>