Enable FontPreloadingDelaysRendering by default on trunk

According to the finch results on M83 Stable and the discussion, all
launch blockers of this feature have been cleared.

This patch first enables it on trunk. A followup internal CL will enable
it in other channels via finch configurations.

Bug: 1040632
Change-Id: Icd9ab4a85c9d755072310c1be4fc4e524133d6f4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2296280Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Reviewed-by: Brian White <bcwhite@chromium.org>
Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#789825}

testing/variations/fieldtrial_testing_config.json

@@ -2790,29 +2790,6 @@
             ]
         }
     ],
-    "FontPreloadingDelaysRendering": [
-        {
-            "platforms": [
-                "android",
-                "android_webview",
-                "chromeos",
-                "linux",
-                "mac",
-                "windows"
-            ],
-            "experiments": [
-                {
-                    "name": "EnabledWithDelay150ms",
-                    "params": {
-                        "delay-in-ms": "150"
-                    },
-                    "enable_features": [
-                        "FontPreloadingDelaysRendering"
-                    ]
-                }
-            ]
-        }
-    ],
     "FontSrcLocalMatching": [
         {
             "platforms": [

third_party/blink/common/features.cc

@@ -558,13 +558,10 @@ const base::Feature kLinkDisabledNewSpecBehavior{
 // they don't miss the first paint if they can be loaded fast enough (e.g.,
 // from the disk cache)
 const base::Feature kFontPreloadingDelaysRendering{
-    "FontPreloadingDelaysRendering", base::FEATURE_DISABLED_BY_DEFAULT};
-
-// Set to be over 90th-percentile of HttpCache.AccessToDone.Used on all
-// platforms, and also to allow some time for IPC and scheduling.
-// TODO(xiaochengh): Tune it for the best performance.
+    "FontPreloadingDelaysRendering", base::FEATURE_ENABLED_BY_DEFAULT};
+// 50ms is the overall best performing value in our experiments.
 const base::FeatureParam<int> kFontPreloadingDelaysRenderingParam{
-    &kFontPreloadingDelaysRendering, "delay-in-ms", 100};
+    &kFontPreloadingDelaysRendering, "delay-in-ms", 50};
 
 const base::Feature kFlexGaps{"FlexGaps", base::FEATURE_DISABLED_BY_DEFAULT};
 const base::Feature kFlexNG{"FlexNG", base::FEATURE_ENABLED_BY_DEFAULT};

third_party/blink/renderer/core/css/font_update_invalidation_test.cc

@@ -111,6 +111,7 @@ TEST_F(FontUpdateInvalidationTest,
 
   // First render the page with the custom font
   font_resource.Complete(ReadAhemWoff2());
+  test::RunPendingTasks();
   Compositor().BeginFrame();
 
   Element* target = GetDocument().getElementById("target");
@@ -208,6 +209,7 @@ TEST_F(FontUpdateInvalidationTest, FallbackBetweenPendingAndLoadedCustomFonts) {
   )HTML");
 
   fast_font_resource.Complete(ReadAhemWoff2());
+  test::RunPendingTasks();
 
   // While slow-font is pending and fast-font is already available, we should
   // use it to render the page.

third_party/blink/web_tests/external/wpt/css/css-fonts/font-display/font-display-ref.html

@@ -27,7 +27,7 @@
  <td></td>
  <td class="arial">a</td>
  <td></td>
- <td></td>
+ <td class="arial">a</td>
 </tr>
 <tr>
  <td>1</td>

third_party/blink/web_tests/external/wpt/css/css-fonts/font-display/font-display.html

@@ -4,6 +4,7 @@
 <meta name="timeout" content="long">
 <link rel="help" href="https://drafts.csswg.org/css-fonts-4/#font-display-desc">
 <link rel="match" href="font-display-ref.html">
+<link rel="preload" href="/fonts/Ahem.ttf?pipe=trickle(d0)" as="font" crossorigin>
 <style>
 .hidden { display: none; }
 </style>

third_party/blink/web_tests/http/tests/webfont/font-display-intervention-expected.html

@@ -27,7 +27,7 @@
  <td></td>
  <td class="arial">a</td>
  <td></td>
- <td></td>
+ <td class="arial">a</td>
 </tr>
 <tr>
  <td>1</td>

third_party/blink/web_tests/http/tests/webfont/font-display-intervention.html

@@ -3,6 +3,7 @@
 <style>
 .hidden { display: none; }
 </style>
+<link rel="preload" href="/resources/Ahem.ttf" as="font" crossorigin>
 <p>Tests how text with a font that takes <i>delay</i> seconds to load look like after <i>T</i> seconds from load start.</p>
 <table id="container">
  <tr>