Fixes Context Hub feature naming and documentation

- Adds "_" in variable name for consistency with feature string
- Adds documentation on what the feature is used for

Bug: 149475852
Test: None
Change-Id: I6eca279df8409de1155cd7014647a705d0d31d6f
diff --git a/api/current.txt b/api/current.txt
index 611fec3..65669cd 100644
--- a/api/current.txt
+++ b/api/current.txt
@@ -12068,7 +12068,7 @@
     field public static final String FEATURE_COMPANION_DEVICE_SETUP = "android.software.companion_device_setup";
     field public static final String FEATURE_CONNECTION_SERVICE = "android.software.connectionservice";
     field public static final String FEATURE_CONSUMER_IR = "android.hardware.consumerir";
-    field public static final String FEATURE_CONTEXTHUB = "android.hardware.context_hub";
+    field public static final String FEATURE_CONTEXT_HUB = "android.hardware.context_hub";
     field public static final String FEATURE_DEVICE_ADMIN = "android.software.device_admin";
     field public static final String FEATURE_EMBEDDED = "android.hardware.type.embedded";
     field public static final String FEATURE_ETHERNET = "android.hardware.ethernet";
diff --git a/core/java/android/content/pm/PackageManager.java b/core/java/android/content/pm/PackageManager.java
index c78d30d..b9a6f2f 100644
--- a/core/java/android/content/pm/PackageManager.java
+++ b/core/java/android/content/pm/PackageManager.java
@@ -1988,10 +1988,11 @@
 
     /**
      * Feature for {@link #getSystemAvailableFeatures} and
-     * {@link #hasSystemFeature}: The device supports a Context Hub.
+     * {@link #hasSystemFeature}: The device supports a Context Hub, used to expose the
+     * functionalities in {@link android.hardware.location.ContextHubManager}.
      */
     @SdkConstant(SdkConstantType.FEATURE)
-    public static final String FEATURE_CONTEXTHUB = "android.hardware.context_hub";
+    public static final String FEATURE_CONTEXT_HUB = "android.hardware.context_hub";
 
     /** {@hide} */
     @SdkConstant(SdkConstantType.FEATURE)
diff --git a/core/java/android/hardware/location/ContextHubManager.java b/core/java/android/hardware/location/ContextHubManager.java
index db16d24..1ed791d 100644
--- a/core/java/android/hardware/location/ContextHubManager.java
+++ b/core/java/android/hardware/location/ContextHubManager.java
@@ -54,7 +54,7 @@
  */
 @SystemApi
 @SystemService(Context.CONTEXTHUB_SERVICE)
-@RequiresFeature(PackageManager.FEATURE_CONTEXTHUB)
+@RequiresFeature(PackageManager.FEATURE_CONTEXT_HUB)
 public final class ContextHubManager {
     private static final String TAG = "ContextHubManager";
 
diff --git a/services/java/com/android/server/SystemServer.java b/services/java/com/android/server/SystemServer.java
index 93662c9..1936f13 100644
--- a/services/java/com/android/server/SystemServer.java
+++ b/services/java/com/android/server/SystemServer.java
@@ -1741,7 +1741,7 @@
             mSystemServiceManager.startService(SensorNotificationService.class);
             t.traceEnd();
 
-            if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_CONTEXTHUB)) {
+            if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_CONTEXT_HUB)) {
                 t.traceBegin("StartContextHubSystemService");
                 mSystemServiceManager.startService(ContextHubSystemService.class);
                 t.traceEnd();