backport patch to fix arm64 build of swiftshader

patches/common/config.json

@@ -5,5 +5,7 @@
 
   "src/electron/patches/common/ffmpeg": "src/third_party/ffmpeg",
 
+  "src/electron/patches/common/swiftshader": "src/third_party/swiftshader",
+
   "src/electron/patches/common/v8":  "src/v8"
 }

patches/common/swiftshader/.patches

@@ -0,0 +1 @@
+fix_arm64.patch

patches/common/swiftshader/fix_arm64.patch

@@ -0,0 +1,38 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Cheng Zhao <[email protected]>
+Date: Thu Dec 6 02:00:06 2018 +0000
+
+Backport fed67899a7b44c9409e94442eaca0deab2f809e3 to fix build on arm64.
+https://swiftshader.googlesource.com/SwiftShader.git/+/fed67899a7b44c9409e94442eaca0deab2f809e3%5E%21/
+
+Can be removed after updating to Chrome 73.
+
+diff --git a/src/Reactor/BUILD.gn b/src/Reactor/BUILD.gn
+index c983c4361..be5e5055d 100644
+--- a/src/Reactor/BUILD.gn
++++ b/src/Reactor/BUILD.gn
+@@ -170,6 +170,9 @@ config("swiftshader_reactor_private_config") {
+     ]
+   } else {
+     cflags = [ "-Wno-unused-local-typedef" ]
++    if(target_cpu == "arm64") {
++      cflags += [ "-Wno-defaulted-function-deleted" ]
++    }
+     defines = [
+       "__STDC_CONSTANT_MACROS",
+       "__STDC_LIMIT_MACROS",
+diff --git a/third_party/llvm-7.0/BUILD.gn b/third_party/llvm-7.0/BUILD.gn
+index 4ccc6d15e..f0b3dc807 100644
+--- a/third_party/llvm-7.0/BUILD.gn
++++ b/third_party/llvm-7.0/BUILD.gn
+@@ -61,6 +61,10 @@ config("swiftshader_llvm_private_config") {
+     }
+   }
+ 
++  if(target_cpu == "arm64") {
++    cflags += [ "-Wno-defaulted-function-deleted" ]
++  }
++
+   cflags += [
+     "-Wno-attributes",
+     "-Wno-deprecated-declarations",