Add an icon to the omnibox when a page is prerendered.

This will only show up for users who have prerendering enabled (mainly via about:flags)

This CL does not include the logic for displaying whether prerender failed on the referring page.

BUG=73065
TEST=Start Chrome with prerendering enabled, go to a page with a <link rel=prefetch> element, navigate to the referred page, and see icon appear.

Review URL: http://codereview.chromium.org/6529031

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@75621 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/content/browser/tab_contents/tab_contents.cc b/content/browser/tab_contents/tab_contents.cc
index 30b91e9..7f8814c 100644
--- a/content/browser/tab_contents/tab_contents.cc
+++ b/content/browser/tab_contents/tab_contents.cc
@@ -279,7 +279,8 @@
       maximum_zoom_percent_(
           static_cast<int>(WebKit::WebView::maxTextSizeMultiplier * 100)),
       temporary_zoom_settings_(false),
-      content_restrictions_(0) {
+      content_restrictions_(0),
+      was_prerendered_(false) {
   renderer_preferences_util::UpdateFromSystemSettings(
       &renderer_preferences_, profile);
 
@@ -1376,6 +1377,8 @@
     if (!is_error_page)
       content_settings_delegate_->ClearCookieSpecificContentSettings();
     content_settings_delegate_->ClearGeolocationContentSettings();
+    // TODO(cbentzel): Should error pages still show prerendered icon?
+    set_was_prerendered(false);
 
     // Check if the URL we are about to load has been prerendered by any chance,
     // and use it if possible.