Switch PluginObserver to use WebContentsUserData.

chrome/browser/plugins/plugin_infobar_delegates.cc

Index: chrome/browser/plugins/plugin_infobar_delegates.cc
diff --git a/chrome/browser/plugins/plugin_infobar_delegates.cc b/chrome/browser/plugins/plugin_infobar_delegates.cc
index 8951eaa13a022b0525d8c7b3c68184b9a40e244a..b3d3569bb5c986baca2191e1630e9b8594ce920c 100644
--- a/chrome/browser/plugins/plugin_infobar_delegates.cc
+++ b/chrome/browser/plugins/plugin_infobar_delegates.cc
@@ -176,7 +176,9 @@ OutdatedPluginInfoBarDelegate::OutdatedPluginInfoBarDelegate(
     PluginObserver* observer,
     PluginInstaller* installer,
     const string16& message)
-    : PluginInfoBarDelegate(InfoBarService::ForTab(observer->tab_contents()),
+    : PluginInfoBarDelegate(
+          InfoBarService::ForTab(
+              TabContents::FromWebContents(observer->web_contents())),
           installer->name(),
           installer->identifier()),
       WeakPluginInstallerObserver(installer),
@@ -233,7 +235,8 @@ bool OutdatedPluginInfoBarDelegate::Accept() {
   if (installer()->url_for_display()) {
     installer()->OpenDownloadURL(web_contents);
   } else {
-    installer()->StartInstalling(observer_->tab_contents());
+    installer()->StartInstalling(
+        TabContents::FromWebContents(observer_->web_contents()));
   }
   return false;
 }