Turn on <link rel=preload> support by default

I2S: https://groups.google.com/a/chromium.org/d/msg/blink-dev/_nu6HlbNQfo/XzaLNb1bBgAJ

BUG=471199

Review URL: https://codereview.chromium.org/1636303003

Cr-Commit-Position: refs/heads/master@{#372037}
diff --git a/third_party/WebKit/LayoutTests/virtual/stable/webexposed/element-instance-property-listing-expected.txt b/third_party/WebKit/LayoutTests/virtual/stable/webexposed/element-instance-property-listing-expected.txt
index 27b5c10..4c485d0 100644
--- a/third_party/WebKit/LayoutTests/virtual/stable/webexposed/element-instance-property-listing-expected.txt
+++ b/third_party/WebKit/LayoutTests/virtual/stable/webexposed/element-instance-property-listing-expected.txt
@@ -637,6 +637,7 @@
     property type
     property value
 html element link
+    property as
     property charset
     property crossOrigin
     property disabled
@@ -646,6 +647,7 @@
     property integrity
     property media
     property rel
+    property relList
     property rev
     property sheet
     property sizes
diff --git a/third_party/WebKit/LayoutTests/virtual/stable/webexposed/global-interface-listing-expected.txt b/third_party/WebKit/LayoutTests/virtual/stable/webexposed/global-interface-listing-expected.txt
index 7cb1098..ea15247 100644
--- a/third_party/WebKit/LayoutTests/virtual/stable/webexposed/global-interface-listing-expected.txt
+++ b/third_party/WebKit/LayoutTests/virtual/stable/webexposed/global-interface-listing-expected.txt
@@ -1960,6 +1960,7 @@
     method constructor
     setter align
 interface HTMLLinkElement : HTMLElement
+    getter as
     getter charset
     getter crossOrigin
     getter disabled
@@ -1969,12 +1970,14 @@
     getter integrity
     getter media
     getter rel
+    getter relList
     getter rev
     getter sheet
     getter sizes
     getter target
     getter type
     method constructor
+    setter as
     setter charset
     setter crossOrigin
     setter disabled
diff --git a/third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in b/third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in
index 57971c9..22e0809 100644
--- a/third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in
+++ b/third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in
@@ -108,7 +108,7 @@
 KeyboardEventKey status=experimental
 LangAttributeAwareFormControlUI
 LinkPreconnect status=stable
-LinkPreload status=experimental
+LinkPreload status=stable
 LinkHeader status=stable
 FractionalScrollOffsets status=experimental
 Media status=stable