Set text-rendering to 'auto' when font shorthand is used in html.css.

There is currently a bug causing invisible tabs whenever text-rendering:
optimizeLegibility is used. Until recently, we (accidentally) over-wrote
the text-rendering property when font shorthands were used, effectively
masking the problem for the matching elements.

This patch adds text-rendering:auto to html.css, for compatibility.

R=timloh@chromium.org
BUG=446405

Review URL: https://codereview.chromium.org/840323002

git-svn-id: svn://svn.chromium.org/blink/trunk@188214 bbb929c8-8fbe-4397-9dbb-9b2b20218538
diff --git a/Source/core/css/html.css b/Source/core/css/html.css
index f49b8d3..9a8052b 100644
--- a/Source/core/css/html.css
+++ b/Source/core/css/html.css
@@ -397,6 +397,7 @@
 input, textarea, keygen, select, button {
     margin: 0__qem;
     font: -webkit-small-control;
+    text-rendering: auto; /* FIXME: Remove when tabs work with optimizeLegibility. */
     color: initial;
     letter-spacing: normal;
     word-spacing: normal;