Added support for building for tvOS

This change is just to add support for building for tvOS.
It is exactly the same as iOS, just using a different SDK.

I had to change the two lines for libjpeg-turbo so that
it will run for both tvOS and iOS.

BUG=skia:

Change-Id: I6ae5fc4257df74c0f321e5d2d71584f6a52ec3a6
Reviewed-on: https://skia-review.googlesource.com/9660
Commit-Queue: Mike Klein <mtklein@chromium.org>
Reviewed-by: Mike Klein <mtklein@chromium.org>
diff --git a/AUTHORS b/AUTHORS
index 376ffd5..f4b36aa 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -26,6 +26,7 @@
 Jeff Muizelaar <jmuizelaar@mozilla.com>
 Lee Salzman <lsalzman@mozilla.com>
 Marcin Kazmierczak <mar.kazmierczak@gmail.com>
+Matthew Leibowitz <mattleibow@live.com>
 MIPS <*@imgtec.com>
 NVIDIA <*@nvidia.com>
 Opera Software ASA <*@opera.com>
diff --git a/gn/BUILD.gn b/gn/BUILD.gn
index 7741354..36c881c 100644
--- a/gn/BUILD.gn
+++ b/gn/BUILD.gn
@@ -50,9 +50,16 @@
 }
 
 if (is_ios) {
-  sdk = "iphoneos"
-  if (target_cpu == "x86" || target_cpu == "x64") {
-    sdk = "iphonesimulator"
+  if (is_tvos) {
+    sdk = "appletvos"
+    if (target_cpu == "x86" || target_cpu == "x64") {
+      sdk = "appletvsimulator"
+    }
+  } else {
+    sdk = "iphoneos"
+    if (target_cpu == "x86" || target_cpu == "x64") {
+      sdk = "iphonesimulator"
+    }
   }
   ios_sysroot = exec_script("find_ios_sysroot.py", [ sdk ], "trim string")
 }
diff --git a/gn/BUILDCONFIG.gn b/gn/BUILDCONFIG.gn
index 6ec5e67..2b3ae33 100644
--- a/gn/BUILDCONFIG.gn
+++ b/gn/BUILDCONFIG.gn
@@ -37,7 +37,8 @@
 
 is_android = current_os == "android"
 is_fuchsia = current_os == "fuchsia"
-is_ios = current_os == "ios"
+is_ios = current_os == "ios" || current_os == "tvos"
+is_tvos = current_os == "tvos"
 is_linux = current_os == "linux"
 is_mac = current_os == "mac"
 is_win = current_os == "win"
diff --git a/third_party/libjpeg-turbo/BUILD.gn b/third_party/libjpeg-turbo/BUILD.gn
index 37b589d..274b02b 100644
--- a/third_party/libjpeg-turbo/BUILD.gn
+++ b/third_party/libjpeg-turbo/BUILD.gn
@@ -67,12 +67,12 @@
       "../externals/libjpeg-turbo/jutils.c",
     ]
 
-    if (current_cpu == "arm" && current_os != "ios") {
+    if (current_cpu == "arm" && !is_ios) {
       sources += [
         "../externals/libjpeg-turbo/simd/jsimd_arm.c",
         "../externals/libjpeg-turbo/simd/jsimd_arm_neon.S",
       ]
-    } else if (current_cpu == "arm64" && current_os != "ios") {
+    } else if (current_cpu == "arm64" && !is_ios) {
       sources += [
         "../externals/libjpeg-turbo/simd/jsimd_arm64.c",
         "../externals/libjpeg-turbo/simd/jsimd_arm64_neon.S",