Enable WebXR Gamepad Module by default

This feature is intended to ship in 79, so the flag should be enabled
by default.

Intent to Ship:
https://groups.google.com/a/chromium.org/d/msg/blink-dev/Nvll21RaKwM/fTn8qUaNBwAJ

Bug: 1013739
Change-Id: I195c07cd61c2058533c2fa6640263567be248a40
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1857008
Commit-Queue: Alexander Cooper <alcooper@chromium.org>
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Reviewed-by: Philip Jägenstedt <foolip@chromium.org>
Cr-Commit-Position: refs/heads/master@{#706576}

content/child/runtime_features.cc

@@ -187,7 +187,7 @@ void SetRuntimeFeaturesFromChromiumFeatures() {
           {wf::EnableWebXRPlaneDetection, features::kWebXrPlaneDetection,
            kEnableOnly},
           {wf::EnableWebXrGamepadModule, features::kWebXrGamepadModule,
-           kEnableOnly},
+           kUseFeatureState},
           {wf::EnableFetchMetadata, network::features::kFetchMetadata,
            kUseFeatureState},
           {wf::EnableFetchMetadataDestination,

content/public/common/content_features.cc

@@ -710,7 +710,7 @@ const base::Feature kWebXrAnchors{"WebXRAnchors",
 
 // Enables access to the WebXR Device API gamepad module.
 const base::Feature kWebXrGamepadModule{"WebXrGamepadModule",
-                                        base::FEATURE_DISABLED_BY_DEFAULT};
+                                        base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Enables access to raycasting against estimated XR scene geometry.
 const base::Feature kWebXrHitTest{"WebXRHitTest",

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -1805,7 +1805,7 @@
     {
       name: "WebXrGamepadModule",
       // depends_on: ["WebXR"],  // TODO(https://crbug.com/954679): uncomment once bug is fixed
-      status: "experimental",
+      status: "stable",
     },
     {
       name: "WebXRHitTest",

third_party/blink/web_tests/virtual/stable/webexposed/global-interface-listing-expected.txt

@@ -8773,6 +8773,7 @@ interface XRFrame
     method getViewerPose
 interface XRInputSource
     attribute @@toStringTag
+    getter gamepad
     getter gripSpace
     getter handedness
     getter profiles