chore: remove mips64el patches as they've largely been upstreamed (#18628)

patches/chromium/sysroot.patch

@@ -0,0 +1,35 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Jeremy Apthorp <nornagon@nornagon.net>
+Date: Thu, 18 Oct 2018 17:03:57 -0700
+Subject: sysroot.patch
+
+Make chrome's install-sysroot scripts point to our custom sysroot builds,
+which include extra deps that Electron needs (e.g. libnotify)
+
+diff --git a/build/linux/sysroot_scripts/install-sysroot.py b/build/linux/sysroot_scripts/install-sysroot.py
+index 858589ae0a6774d6c34a51e1db1ef852f40ad68d..c4a0ac5c9e16a217634602233bd709af6943470e 100755
+--- a/build/linux/sysroot_scripts/install-sysroot.py
++++ b/build/linux/sysroot_scripts/install-sysroot.py
+@@ -32,9 +32,11 @@ import sys
+ import urllib2
+ 
+ SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__))
++SRC_DIR = os.path.dirname(os.path.dirname(os.path.dirname(SCRIPT_DIR)))
++SYSTOORS_CONFIG_DIR = os.path.join(SRC_DIR, 'electron', 'script')
+ 
+-URL_PREFIX = 'https://commondatastorage.googleapis.com'
+-URL_PATH = 'chrome-linux-sysroot/toolchain'
++URL_PREFIX = 'http://s3.amazonaws.com'
++URL_PATH = 'gh-contractor-zcbenz/toolchain'
+ 
+ VALID_ARCHS = ('arm', 'arm64', 'i386', 'amd64', 'mips', 'mips64el')
+ 
+@@ -98,7 +100,7 @@ def GetSysrootDict(target_platform, target_arch):
+   if target_arch not in VALID_ARCHS:
+     raise Error('Unknown architecture: %s' % target_arch)
+ 
+-  sysroots_file = os.path.join(SCRIPT_DIR, 'sysroots.json')
++  sysroots_file = os.path.join(SYSTOORS_CONFIG_DIR, 'sysroots.json')
+   sysroots = json.load(open(sysroots_file))
+   sysroot_key = '%s_%s' % (target_platform, target_arch)
+   if sysroot_key not in sysroots: