Plugin Power Saver: Record PPS UMAs only for users with PPS enabled.

chrome/renderer/chrome_content_renderer_client.cc

Index: chrome/renderer/chrome_content_renderer_client.cc
diff --git a/chrome/renderer/chrome_content_renderer_client.cc b/chrome/renderer/chrome_content_renderer_client.cc
index e4ea3df086ac26fcb2e705b2ccc6588a8e443614..be1dcf7fcc90682c92479dec688fe5e547b883b2 100644
--- a/chrome/renderer/chrome_content_renderer_client.cc
+++ b/chrome/renderer/chrome_content_renderer_client.cc
@@ -890,9 +890,9 @@ WebPlugin* ChromeContentRendererClient::CreatePlugin(
           break;
         }
 
-        scoped_ptr<content::PluginInstanceThrottler> throttler =
-            PluginInstanceThrottler::Create(power_saver_enabled);
+        scoped_ptr<content::PluginInstanceThrottler> throttler;
         if (power_saver_enabled) {
+          throttler = PluginInstanceThrottler::Create();
           // PluginPreroller manages its own lifetime.
           new PluginPreroller(
               render_frame, frame, params, info, identifier, group_name,