Make themes in the incognito NTP which are bottom-aligned attach to the botto...

chrome/browser/resources/new_incognito_tab_theme.css

Index: chrome/browser/resources/new_incognito_tab_theme.css
===================================================================
--- chrome/browser/resources/new_incognito_tab_theme.css	(revision 25903)
+++ chrome/browser/resources/new_incognito_tab_theme.css	(working copy)
@@ -1,11 +1,13 @@
 html {
-  background-image:url(chrome://theme/theme_ntp_background?$1);
-  background-color:$2;
-  background-position:$3;
-  background-repeat:$5;
-  overflow:hidden;
+  background-image: url(chrome://theme/theme_ntp_background?$1);
+  background-color: $2;
+  background-position: $3;
+  background-repeat: $5;
+  height: 100%;
+  overflow: auto;
+  background-attachment: fixed;
 }
 
 html[bookmarkbarattached='true'] {
-  background-position:$4;
-}
+  background-position: $4;
+}