Handle initial values in background-repeat introduced by the background shorthand

background-repeat serialization did not handle initial keyword values in
background-repeat value lists.
Initial values in value lists are introduced by setting the background
shorthand to multiple background values while omitting background-repeat
properties.
Example: background: url(#1), url(#2), url(#3);
The background-repeat gets stored internally as "initial, initial, initial".

This patch updates StylePropertySerializer::backgroundRepeatPropertyValue()
to handle this case correctly.

BUG=378167

Review URL: https://codereview.chromium.org/303993003

git-svn-id: svn://svn.chromium.org/blink/trunk@175261 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/LayoutTests/fast/css/background-repeat-serialize.html

@@ -34,6 +34,13 @@ test(function() {
   // FIXME (crbug.com/376179): Make setting background-repeat-x/y to multiple values work on CSSStyleDeclarations.
   // assert_equals(serialize('background-repeat-x: repeat, no-repeat; background-repeat-y: no-repeat, repeat, no-repeat'),
   //   'repeat-x, repeat-y, repeat-x, no-repeat, repeat, no-repeat');
-  assert_equals(serialize('background-repeat: repeat, no-repeat, repeat; background-repeat-y: no-repeat'), 'repeat-x, no-repeat, repeat-x');
+  assert_equals(serialize('background-repeat: repeat, no-repeat, repeat; background-repeat-y: no-repeat;'), 'repeat-x, no-repeat, repeat-x');
 }, 'Mismatched value lengths should repeat to their lowest common multiple');
+
+test(function() {
+  assert_equals(serialize('background: url(#1), url(#2), url(#3);'), 'repeat, repeat, repeat');
+  assert_equals(serialize('background: repeat-x, repeat-y, url(#);'), 'repeat-x, repeat-y, repeat');
+  assert_equals(serialize('background: url(#), no-repeat; background-repeat-x: no-repeat'), 'repeat-y, no-repeat');
+  assert_equals(serialize('background: url(#), no-repeat; background-repeat-y: no-repeat'), 'repeat-x, no-repeat');
+}, 'Initial values introduced by the background shorthand should be handled as repeat.');
 </script>

third_party/WebKit/Source/core/css/StylePropertySerializer.cpp

@@ -702,20 +702,24 @@ String StylePropertySerializer::borderPropertyValue(CommonValueMode valueMode) c
     return result.isEmpty() ? String() : result.toString();
 }
 
-static void buildSingleBackgroundRepeatValue(StringBuilder& builder, const CSSValue& repeatXValue, const CSSValue& repeatYValue)
+static void appendBackgroundRepeatValue(StringBuilder& builder, const CSSValue& repeatXCSSValue, const CSSValue& repeatYCSSValue)
 {
-    CSSValueID repeatXValueId = toCSSPrimitiveValue(repeatXValue).getValueID();
-    CSSValueID repeatYValueId = toCSSPrimitiveValue(repeatYValue).getValueID();
+    // FIXME: Ensure initial values do not appear in CSS_VALUE_LISTS.
+    DEFINE_STATIC_REF_WILL_BE_PERSISTENT(CSSPrimitiveValue, initialRepeatValue, CSSPrimitiveValue::create(CSSValueRepeat));
+    const CSSPrimitiveValue& repeatX = repeatXCSSValue.isInitialValue() ? *initialRepeatValue : toCSSPrimitiveValue(repeatXCSSValue);
+    const CSSPrimitiveValue& repeatY = repeatYCSSValue.isInitialValue() ? *initialRepeatValue : toCSSPrimitiveValue(repeatYCSSValue);
+    CSSValueID repeatXValueId = repeatX.getValueID();
+    CSSValueID repeatYValueId = repeatY.getValueID();
     if (repeatXValueId == repeatYValueId) {
-        builder.append(repeatXValue.cssText());
+        builder.append(repeatX.cssText());
     } else if (repeatXValueId == CSSValueNoRepeat && repeatYValueId == CSSValueRepeat) {
         builder.append("repeat-y");
     } else if (repeatXValueId == CSSValueRepeat && repeatYValueId == CSSValueNoRepeat) {
         builder.append("repeat-x");
     } else {
-        builder.append(repeatXValue.cssText());
+        builder.append(repeatX.cssText());
         builder.append(" ");
-        builder.append(repeatYValue.cssText());
+        builder.append(repeatY.cssText());
     }
 }
 
@@ -757,7 +761,7 @@ String StylePropertySerializer::backgroundRepeatPropertyValue() const
     for (size_t i = 0; i < shorthandLength; ++i) {
         if (i)
             builder.append(", ");
-        buildSingleBackgroundRepeatValue(builder,
+        appendBackgroundRepeatValue(builder,
             *repeatXList->item(i % repeatXList->length()),
             *repeatYList->item(i % repeatYList->length()));
     }