Support MAS build

chromiumcontent/BUILD.gn

@@ -367,3 +367,10 @@ config("build_time_executable") {
     configs += [ "//build/config/gcc:rpath_for_built_shared_libraries" ]
   }
 }
+
+# For MAS build, we force defining "MAS_BUILD".
+config("mas_build") {
+  if (getenv("MAS_BUILD") != "") {
+    defines = [ "MAS_BUILD" ]
+  }
+}

patches/build_gn.patch

@@ -1,5 +1,5 @@
 diff --git a/build/config/BUILDCONFIG.gn b/build/config/BUILDCONFIG.gn
-index 6390ae91725b..a2d87c5fdcd6 100644
+index 6390ae9..b113ecd 100644
 --- a/build/config/BUILDCONFIG.gn
 +++ b/build/config/BUILDCONFIG.gn
 @@ -123,6 +123,8 @@ if (current_os == "") {
@@ -11,8 +11,16 @@ index 6390ae91725b..a2d87c5fdcd6 100644
    # 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
+@@ -477,6 +479,7 @@ default_compiler_configs = [
+   "//build/config/compiler:no_rtti",
+   "//build/config/compiler:runtime_library",
+   "//build/config/sanitizers:default_sanitizer_flags",
++  "//chromiumcontent:mas_build",
+ ]
+ if (is_win) {
+   default_compiler_configs += [
 diff --git a/third_party/widevine/cdm/BUILD.gn b/third_party/widevine/cdm/BUILD.gn
-index e5fdb29e858f..30040737dbb4 100644
+index e5fdb29..3004073 100644
 --- a/third_party/widevine/cdm/BUILD.gn
 +++ b/third_party/widevine/cdm/BUILD.gn
 @@ -93,7 +93,7 @@ if (widevine_cdm_binary_files != []) {
@@ -25,7 +33,7 @@ index e5fdb29e858f..30040737dbb4 100644
          # Not to strip important symbols by -Wl,-dead_strip.
          "-Wl,-exported_symbol,_PPP_GetInterface",
 diff --git a/third_party/WebKit/Source/platform/BUILD.gn b/third_party/WebKit/Source/platform/BUILD.gn
-index ce25028fe74f..9a887e3c163a 100644
+index ce25028..9a887e3 100644
 --- a/third_party/WebKit/Source/platform/BUILD.gn
 +++ b/third_party/WebKit/Source/platform/BUILD.gn
 @@ -174,6 +174,7 @@ action("character_data") {