Add a feature flag for controlling Android downloadable fonts matching

Wire it from content::features to a Blink RuntimeEnabledFeature in order
to enable potential A/B testing for this font retrieval path.

Bug: 1115064
Change-Id: I81fb92591b7a78b3a136205d4863a423e003ab9b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2416380Reviewed-by: Stephen Chenney <schenney@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Dominik Röttsches <drott@chromium.org>
Cr-Commit-Position: refs/heads/master@{#808284}

content/child/runtime_features.cc

@@ -358,6 +358,8 @@ void SetRuntimeFeaturesFromChromiumFeatures() {
            kEnableOnly},
           {"AllowContentInitiatedDataUrlNavigations",
            features::kAllowContentInitiatedDataUrlNavigations, kDefault},
+          {"AndroidDownloadableFontsMatching",
+           features::kAndroidDownloadableFontsMatching, kDefault},
           {"AudioWorkletRealtimeThread",
            blink::features::kAudioWorkletRealtimeThread, kEnableOnly},
           {"BlockCredentialedSubresources",

content/public/common/content_features.cc

@@ -41,6 +41,11 @@ const base::Feature kAllowSignedHTTPExchangeCertsWithoutExtension{
     "AllowSignedHTTPExchangeCertsWithoutExtension",
     base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Allows Blink to request fonts from the Android Downloadable Fonts API through
+// the service implemented on the Java side.
+const base::Feature kAndroidDownloadableFontsMatching{
+    "AndroidDownloadableFontsMatching", base::FEATURE_ENABLED_BY_DEFAULT};
+
 // Launches the audio service on the browser startup.
 const base::Feature kAudioServiceLaunchOnStartup{
     "AudioServiceLaunchOnStartup", base::FEATURE_DISABLED_BY_DEFAULT};

content/public/common/content_features.h

@@ -20,6 +20,7 @@ CONTENT_EXPORT extern const base::Feature kAllowActivationDelegationAttr;
 CONTENT_EXPORT extern const base::Feature
     kAllowContentInitiatedDataUrlNavigations;
 CONTENT_EXPORT extern const base::Feature kAllowPopupsDuringPageUnload;
+CONTENT_EXPORT extern const base::Feature kAndroidDownloadableFontsMatching;
 CONTENT_EXPORT extern const base::Feature
     kAllowSignedHTTPExchangeCertsWithoutExtension;
 CONTENT_EXPORT extern const base::Feature kAudioServiceLaunchOnStartup;

third_party/blink/renderer/platform/fonts/android/font_unique_name_lookup_android.cc

@@ -84,11 +84,17 @@ sk_sp<SkTypeface> FontUniqueNameLookupAndroid::MatchUniqueName(
       MatchUniqueNameFromFirmwareFonts(font_unique_name);
   if (result_font)
     return result_font;
-  return MatchUniqueNameFromDownloadableFonts(font_unique_name);
+  if (RuntimeEnabledFeatures::AndroidDownloadableFontsMatchingEnabled()) {
+    return MatchUniqueNameFromDownloadableFonts(font_unique_name);
+  } else {
+    return nullptr;
+  }
 }
 
 void FontUniqueNameLookupAndroid::EnsureServiceConnected() {
-  if (firmware_font_lookup_service_ && android_font_lookup_service_)
+  if (firmware_font_lookup_service_ &&
+      (!RuntimeEnabledFeatures::AndroidDownloadableFontsMatchingEnabled() ||
+       android_font_lookup_service_))
     return;
 
   if (!firmware_font_lookup_service_) {
@@ -96,7 +102,8 @@ void FontUniqueNameLookupAndroid::EnsureServiceConnected() {
         firmware_font_lookup_service_.BindNewPipeAndPassReceiver());
   }
 
-  if (!android_font_lookup_service_) {
+  if (RuntimeEnabledFeatures::AndroidDownloadableFontsMatchingEnabled() &&
+      !android_font_lookup_service_) {
     Platform::Current()->GetBrowserInterfaceBroker()->GetInterface(
         android_font_lookup_service_.BindNewPipeAndPassReceiver());
   }

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -150,6 +150,9 @@
       name: "AllowSyncXHRInPageDismissal",
       origin_trial_feature_name: "AllowSyncXHRInPageDismissal",
     },
+    {
+      name: "AndroidDownloadableFontsMatching",
+    },
     {
       name: "AnimationWorklet",
       status: "experimental",