build: define is_mas_build as a GN arg

This is to support the GN build, which won't read the MAS_BUILD
environment variable, and will instead rely on the GN args system to
toggle between MAS/non-MAS.

chromiumcontent/args/ffmpeg.gn

@@ -1,5 +1,6 @@
 root_extra_deps = [ "//libchromiumcontent/chromiumcontent" ]
 is_component_build = false
+is_mas_build = getenv("MAS_BUILD") != ""
 is_debug = false
 enable_nacl = false
 enable_widevine = true

chromiumcontent/args/native_mksnapshot.gn

@@ -1,5 +1,6 @@
 root_extra_deps = [ "//v8:v8_maybe_snapshot" ]
 is_electron_build = true
+is_mas_build = getenv("MAS_BUILD") != ""
 is_component_build = false
 is_debug = false
 enable_linux_installer = false

chromiumcontent/args/shared_library.gn

@@ -1,6 +1,7 @@
 root_extra_deps = [ "//libchromiumcontent/chromiumcontent" ]
 is_electron_build = true
 is_component_build = true
+is_mas_build = getenv("MAS_BUILD") != ""
 is_debug = true
 symbol_level = 2
 use_allocator = "none"    # on Linux this defaults to "tcmalloc", but tcmalloc deadlocks when Electron CI tests are run inside Docker

chromiumcontent/args/static_library.gn

@@ -1,6 +1,7 @@
 root_extra_deps = [ "//libchromiumcontent/chromiumcontent" ]
 is_electron_build = true
 is_component_build = false
+is_mas_build = getenv("MAS_BUILD") != ""
 is_official_build = true
 symbol_level = 2
 enable_nacl = false

chromiumcontent/args/tests.gn

@@ -1,6 +1,7 @@
 root_extra_deps = [ "//libchromiumcontent/chromiumcontent:chromiumcontent_tests" ]
 is_debug = false
 is_electron_build = true
+is_mas_build = getenv("MAS_BUILD") != ""
 is_component_build = true
 dcheck_always_on = true
 symbol_level = 1

chromiumcontent/config/BUILD.gn

@@ -23,7 +23,7 @@ config("build_time_executable") {
 
 # For MAS build, we force defining "MAS_BUILD".
 config("mas_build") {
-  if (getenv("MAS_BUILD") != "") {
+  if (is_mas_build) {
     defines = [ "MAS_BUILD" ]
   }
 }

patches/common/chromium/build_gn.patch

@@ -1,18 +1,32 @@
+diff --git a/.gn b/.gn
+index 50a8a2fe9f1e..66ced79f1627 100644
+--- a/.gn
++++ b/.gn
+@@ -259,4 +259,8 @@ exec_script_whitelist =
+       # Not gypi-to-gn.
+       "//google_apis/BUILD.gn",
+       "//printing/BUILD.gn",
++      # While electron transitions to GN, we use gypi_to_gn to synchronize
++      # file lists
++      "//electron/BUILD.gn",
++      "//electron/brightray/BUILD.gn",
+     ]
 diff --git a/build/config/BUILDCONFIG.gn b/build/config/BUILDCONFIG.gn
-index de3f35f124aa..a52003f1b5e1 100644
+index 7d60dd920904..d2f2cbc99915 100644
 --- a/build/config/BUILDCONFIG.gn
 +++ b/build/config/BUILDCONFIG.gn
-@@ -123,6 +123,9 @@ if (current_os == "") {
+@@ -123,6 +123,10 @@ if (current_os == "") {
  #   even if the value is overridden, which is wasteful. See first bullet.
  
  declare_args() {
 +  is_electron_build = false
 +  is_electron_gn_build = false
++  is_mas_build = false
 +
    # Set to enable the official build level of optimization. This has nothing
    # to do with branding, but enables an additional level of optimization above
    # release (!is_debug). This might be better expressed as a tri-state
-@@ -529,6 +529,7 @@ default_compiler_configs = [
+@@ -534,6 +538,7 @@ default_compiler_configs = [
    "//build/config/compiler:runtime_library",
    "//build/config/coverage:default_coverage",
    "//build/config/sanitizers:default_sanitizer_flags",
@@ -20,7 +34,7 @@ index de3f35f124aa..a52003f1b5e1 100644
  ]
  if (is_win) {
    default_compiler_configs += [
-@@ -642,6 +645,7 @@ template("component") {
+@@ -660,6 +665,7 @@ template("component") {
      _component_mode = "shared_library"
    } else if (defined(invoker.static_component_type)) {
      assert(invoker.static_component_type == "static_library" ||
@@ -29,10 +43,10 @@ index de3f35f124aa..a52003f1b5e1 100644
      _component_mode = invoker.static_component_type
    } else if (is_android || !defined(invoker.sources)) {
 diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
-index 7888e2f8589d..b95cef9596d4 100644
+index 9a10137aa405..bb33e5450eaa 100644
 --- a/build/config/compiler/BUILD.gn
 +++ b/build/config/compiler/BUILD.gn
-@@ -553,10 +553,13 @@ config("compiler") {
+@@ -579,10 +579,13 @@ config("compiler") {
        ldflags += [ "-Wl,--lto-O0" ]
      }
  
@@ -51,10 +65,10 @@ index 7888e2f8589d..b95cef9596d4 100644
      # Work-around for http://openradar.appspot.com/20356002
      if (is_mac) {
 diff --git a/build/config/win/BUILD.gn b/build/config/win/BUILD.gn
-index 5e1f7fcc4d83..15723e6b7184 100644
+index 1f6bc13e087f..4630045ff554 100644
 --- a/build/config/win/BUILD.gn
 +++ b/build/config/win/BUILD.gn
-@@ -276,7 +276,7 @@ config("common_linker_setup") {
+@@ -314,7 +314,7 @@ config("cfi_linker") {
  # See https://msdn.microsoft.com/en-us/library/2kzt1wy3.aspx for a reference of
  # what each value does.
  config("default_crt") {
@@ -64,10 +78,10 @@ index 5e1f7fcc4d83..15723e6b7184 100644
      # exceptions or will give errors about things not matching, so keep
      # exceptions on.
 diff --git a/third_party/WebKit/Source/platform/BUILD.gn b/third_party/WebKit/Source/platform/BUILD.gn
-index 6c86a6454256..2bc8c31396af 100644
+index dc6e613e7c7e..36abbd583faf 100644
 --- a/third_party/WebKit/Source/platform/BUILD.gn
 +++ b/third_party/WebKit/Source/platform/BUILD.gn
-@@ -160,6 +160,7 @@ action("instrumentation_probes") {
+@@ -135,6 +135,7 @@ action("instrumentation_probes") {
  }
  
  executable("character_data_generator") {
@@ -75,16 +89,3 @@ index 6c86a6454256..2bc8c31396af 100644
    sources = [
      "text/CharacterPropertyDataGenerator.cpp",
      "text/CharacterPropertyDataGenerator.h",
-diff --git a/.gn b/.gn
-index 9e744b9940e2..09208f2e98fa 100644
---- a/.gn
-+++ b/.gn
-@@ -245,4 +245,8 @@ exec_script_whitelist =
-       # Not gypi-to-gn.
-       "//google_apis/BUILD.gn",
-       "//printing/BUILD.gn",
-+      # While electron transitions to GN, we use gypi_to_gn to synchronize
-+      # file lists
-+      "//electron/BUILD.gn",
-+      "//electron/brightray/BUILD.gn",
-     ]