Ship CSS gradient color stop double-position syntax

Intent-to-Ship thread:

 https://groups.google.com/a/chromium.org/forum/#!msg/blink-dev/8B9FbeTBIK0/DNkC2pz-AAAJ

Also removing the actual feature and corresponding check, because it's
only used in a single spot, so if the feature should need to be
unshipped it ought to be a fairly trivial revert.

Bug: 707047, 880733
Change-Id: Ie854d7fd9f7a22e9c6144668a37f694dd1c508ee
Reviewed-on: https://chromium-review.googlesource.com/1230018Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Fredrik Söderquist <fs@opera.com>
Cr-Commit-Position: refs/heads/master@{#592028}

third_party/blink/renderer/core/css/parser/css_property_parser_helpers.cc

@@ -1170,16 +1170,14 @@ static bool ConsumeGradientColorStops(CSSParserTokenRange& range,
       return false;
     gradient->AddStop(stop);
 
-    if (RuntimeEnabledFeatures::MultipleColorStopPositionsEnabled()) {
-      if (!stop.color_ || !stop.offset_)
-        continue;
+    if (!stop.color_ || !stop.offset_)
+      continue;
 
-      // Optional second position.
-      stop.offset_ = consume_position_func(range, context, kValueRangeAll,
-                                           UnitlessQuirk::kForbid);
-      if (stop.offset_)
-        gradient->AddStop(stop);
-    }
+    // Optional second position.
+    stop.offset_ = consume_position_func(range, context, kValueRangeAll,
+                                         UnitlessQuirk::kForbid);
+    if (stop.offset_)
+      gradient->AddStop(stop);
   } while (ConsumeCommaIncludingWhitespace(range));
 
   // The last color stop cannot be a color hint.

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -780,10 +780,6 @@
       name: "MojoJSTest",
       status: "test",
     },
-    {
-      name: "MultipleColorStopPositions",
-      status: "experimental",
-    },
     {
       name: "NavigatorContentUtils",
     },