--- a/netwerk/protocol/http/nsHttpHandler.cpp
+++ b/netwerk/protocol/http/nsHttpHandler.cpp
@@ -121,16 +121,28 @@ NewURI(const nsACString &aSpec,
     if (NS_FAILED(rv)) {
         return rv;
     }
 
     url.forget(aURI);
     return NS_OK;
 }
 
+static nsCString
+GetDeviceModelId() {
+    nsCOMPtr<nsIPropertyBag2> infoService = do_GetService("@mozilla.org/system-info;1");
+    MOZ_ASSERT(infoService, "Could not find a system info service");
+    nsAutoString androidDevice;
+    nsresult rv = infoService->GetPropertyAsAString(NS_LITERAL_STRING("device"), androidDevice);
+    if (NS_SUCCEEDED(rv)) {
+        return NS_LossyConvertUTF16toASCII(androidDevice);
+    }
+    return EmptyCString();
+}
+
 //-----------------------------------------------------------------------------
 // nsHttpHandler <public>
 //-----------------------------------------------------------------------------
 
 nsHttpHandler *gHttpHandler = nullptr;
 
 nsHttpHandler::nsHttpHandler()
     : mHttpVersion(NS_HTTP_VERSION_1_1)
@@ -774,16 +786,20 @@ nsHttpHandler::InitUserAgentComponents()
         bool isTV;
         rv = infoService->GetPropertyAsBool(NS_LITERAL_STRING("tv"), &isTV);
         if (NS_SUCCEEDED(rv) && isTV) {
             mCompatDevice.AssignLiteral("TV");
         } else {
             mCompatDevice.AssignLiteral("Mobile");
         }
     }
+
+    if (Preferences::GetBool(UA_PREF("use_device"), false)) {
+        mDeviceModelId = mozilla::net::GetDeviceModelId();
+    }
 #endif // ANDROID
 
 #ifdef MOZ_MULET
     {
         // Add the `Mobile` or `Tablet` or `TV` token when running in the b2g
         // desktop simulator via preference.
         nsCString deviceType;
         nsresult rv = Preferences::GetCString("devtools.useragent.device_type", &deviceType);
@@ -952,16 +968,28 @@ nsHttpHandler::PrefsChanged(nsIPrefBranc
 
     // general.useragent.override
     if (PREF_CHANGED(UA_PREF("override"))) {
         prefs->GetCharPref(UA_PREF("override"),
                             getter_Copies(mUserAgentOverride));
         mUserAgentIsDirty = true;
     }
 
+#ifdef ANDROID
+    // general.useragent.use_device
+    if (PREF_CHANGED(UA_PREF("use_device"))) {
+        if (Preferences::GetBool(UA_PREF("use_device"), false)) {
+            mDeviceModelId = mozilla::net::GetDeviceModelId();
+        } else {
+            mDeviceModelId = EmptyCString();
+        }
+        mUserAgentIsDirty = true;
+    }
+#endif
+
     //
     // HTTP options
     //
 
     if (PREF_CHANGED(HTTP_PREF("keep-alive.timeout"))) {
         rv = prefs->GetIntPref(HTTP_PREF("keep-alive.timeout"), &val);
         if (NS_SUCCEEDED(rv))
             mIdleTimeout = PR_SecondsToInterval(clamped(val, 1, 0xffff));