Revert 168577 "Remove spurious check for invalid value."

> Remove spurious check for invalid value.
> 
> The isCSSPrimitiveValue check is likely covering up parser bugs,
> and toCSSPrimitiveValue has the assert to ensure we're not
> doing something bad.
> 
> R=eae,ksakamoto@chromium.org,timloh@chromium.org
> BUG=
> 
> Review URL: https://codereview.chromium.org/184103034

BUG=350509
TBR=dglazkov@chromium.org

Review URL: https://codereview.chromium.org/203583004

git-svn-id: svn://svn.chromium.org/blink/trunk@169456 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/build/scripts/templates/StyleBuilder.cpp.tmpl

@@ -59,6 +59,8 @@ void StyleBuilderFunctions::applyValue{{property_id}}(StyleResolverState& state,
 {%- if property.converter %}
     {{ set_value(property) }}(StyleBuilderConverter::{{property.converter}}(state, value));
 {%- elif property.font %}
+    if (!value->isPrimitiveValue())
+        return;
     {{ set_value(property) }}(static_cast<{{property.type_name}}>(*toCSSPrimitiveValue(value)));
 {%- else %}
     {{ set_value(property) }}(static_cast<{{property.type_name}}>(*toCSSPrimitiveValue(value)));