linux_chromiumos_3_18: remove kernel due lack of maintainer/breakage

There is no maintainer for this package, probably not many users.
It requires effort to fix all third-party modules for this old kernel
versions. It might contain unpatched security holes.

For Pixel chromebooks, we have the samus-kernel.
Apart from that https://github.com/GalliumOS/linux might be a good choice.

pkgs/os-specific/linux/kernel/common-config.nix

@@ -202,7 +202,7 @@ with stdenv.lib;
 
   # Video configuration.
   # Enable KMS for devices whose X.org driver supports it.
-  ${optionalString (versionOlder version "4.3" && !(features.chromiumos or false)) ''
+  ${optionalString (versionOlder version "4.3") ''
     DRM_I915_KMS y
   ''}
   # Allow specifying custom EDID on the kernel command line
@@ -566,9 +566,7 @@ with stdenv.lib;
   MEDIA_CAMERA_SUPPORT y
   MEDIA_RC_SUPPORT y
   MEDIA_USB_SUPPORT y
-  ${optionalString (!(features.chromiumos or false)) ''
-    MEDIA_PCI_SUPPORT y
-  ''}
+  MEDIA_PCI_SUPPORT y
 
   # Our initrd init uses shebang scripts, so can't be modular.
   BINFMT_SCRIPT y
@@ -662,67 +660,6 @@ with stdenv.lib;
     WW_MUTEX_SELFTEST? n
   ''}
 
-  # ChromiumOS support
-  ${optionalString (features.chromiumos or false) ''
-    CHROME_PLATFORMS y
-    VGA_SWITCHEROO n
-    MMC_SDHCI_PXAV2 n
-    NET_IPVTI n
-    IPV6_VTI n
-    REGULATOR_FIXED_VOLTAGE n
-    TPS6105X n
-    CPU_FREQ_STAT y
-    IPV6 y
-    MFD_CROS_EC y
-    MFD_CROS_EC_LPC y
-    MFD_CROS_EC_DEV y
-    CHARGER_CROS_USB_PD y
-    I2C y
-    MEDIA_SUBDRV_AUTOSELECT n
-    VIDEO_IR_I2C n
-    BLK_DEV_DM y
-    ANDROID_PARANOID_NETWORK n
-    DM_VERITY n
-    DRM_VGEM n
-    CPU_FREQ_GOV_INTERACTIVE n
-    INPUT_KEYRESET n
-    DM_BOOTCACHE n
-    UID_CPUTIME n
-
-    ${optionalString (versionAtLeast version "3.18") ''
-      CPUFREQ_DT n
-      EXTCON_CROS_EC n
-      DRM_POWERVR_ROGUE n
-      CHROMEOS_OF_FIRMWARE y
-      TEST_RHASHTABLE n
-      BCMDHD n
-      TRUSTY n
-    ''}
-
-    ${optionalString (versionOlder version "3.18") ''
-      MALI_MIDGARD n
-      DVB_USB_DIB0700 n
-      DVB_USB_DW2102 n
-      DVB_USB_PCTV452E n
-      DVB_USB_TTUSB2 n
-      DVB_USB_AF9015 n
-      DVB_USB_AF9035 n
-      DVB_USB_ANYSEE n
-      DVB_USB_AZ6007 n
-      DVB_USB_IT913X n
-      DVB_USB_LME2510 n
-      DVB_USB_RTL28XXU n
-      USB_S2255 n
-      VIDEO_EM28XX n
-      VIDEO_TM6000 n
-      USB_DWC2 n
-      USB_GSPCA n
-      SPEAKUP n
-      XO15_EBOOK n
-      USB_GADGET n
-    ''}
-  ''}
-
   ${kernelPlatform.kernelExtraConfig or ""}
   ${extraConfig}
 ''