[css-flex] Enable aspect-ratio item bug fixes

Also add a finch flag in case we need to kill it. There have been 0 bugs
reported against these bugfixes from folks running with experimental web
platform features, so I doubt we'll need the kill switch.

out/Release/chrome shows the bugfixes
out/Release/chrome --disable-features=FlexAspectRatio doesn't show them

Change-Id: I875f3ca1f34bee680c4c94035247cb6ff6adf385
Bug: 1132627
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2433630
Commit-Queue: David Grogan <dgrogan@chromium.org>
Reviewed-by: Christian Biesinger <cbiesinger@chromium.org>
Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#811589}

content/child/runtime_features.cc

@@ -344,6 +344,7 @@ void SetRuntimeFeaturesFromChromiumFeatures() {
           {"FeaturePolicyForClientHints",
            features::kFeaturePolicyForClientHints},
           {"EditingNG", blink::features::kEditingNG},
+          {"FlexAspectRatio", blink::features::kFlexAspectRatio},
           {"FontAccess", blink::features::kFontAccess},
           {"FontSrcLocalMatching", features::kFontSrcLocalMatching},
           {"ForceSynchronousHTMLParsing",

third_party/blink/common/features.cc

@@ -567,6 +567,8 @@ const base::Feature kFontPreloadingDelaysRendering{
 const base::FeatureParam<int> kFontPreloadingDelaysRenderingParam{
     &kFontPreloadingDelaysRendering, "delay-in-ms", 50};
 
+const base::Feature kFlexAspectRatio{"FlexAspectRatio",
+                                     base::FEATURE_ENABLED_BY_DEFAULT};
 const base::Feature kFlexNG{"FlexNG", base::FEATURE_ENABLED_BY_DEFAULT};
 
 const base::Feature kKeepScriptResourceAlive{"KeepScriptResourceAlive",

third_party/blink/public/common/features.h

@@ -177,6 +177,7 @@ BLINK_COMMON_EXPORT extern const base::Feature kFontPreloadingDelaysRendering;
 BLINK_COMMON_EXPORT extern const base::FeatureParam<int>
     kFontPreloadingDelaysRenderingParam;
 
+BLINK_COMMON_EXPORT extern const base::Feature kFlexAspectRatio;
 BLINK_COMMON_EXPORT extern const base::Feature kFlexNG;
 
 BLINK_COMMON_EXPORT extern const base::Feature kKeepScriptResourceAlive;

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -825,7 +825,7 @@
     },
     {
       name: "FlexAspectRatio",
-      status: "experimental",
+      status: "stable",
     },
     {
       name: "FocuslessSpatialNavigation",