[Bindings] Create and use V8 context snapshots

gin/BUILD.gn

Index: gin/BUILD.gn
diff --git a/gin/BUILD.gn b/gin/BUILD.gn
index eaf88a8c77da16cc5e773b3f2dc5dca8ab85157c..b8ed4313977f31d68e57793784cd5c4525d00e83 100644
--- a/gin/BUILD.gn
+++ b/gin/BUILD.gn
@@ -110,6 +110,66 @@ executable("gin_shell") {
   configs += [ "//v8:external_startup_data" ]
 }
 
+group("blink_v8_snapshot") {
+  public_deps = [
+    ":generate_blink_v8_snapshot",
+  ]
+}
+
+action("generate_blink_v8_snapshot") {
+  script = "run.py"
+  output_file = "$root_out_dir/blink_v8_snapshot.bin"
+  output_path = rebase_path(output_file, root_build_dir)
+
+  args = [
+    "./" + rebase_path(
+            get_label_info(":blink_v8_snapshot_generator($host_toolchain)",
+                           "root_out_dir") + "/blink_v8_snapshot_generator",
+            root_build_dir),
+    "--output_file=$output_path",
+  ]
+
+  outputs = [
+    output_file,
+  ]
+
+  deps = [
+    ":blink_v8_snapshot_generator($host_toolchain)",
+  ]
+}
+
+# This config disables a link time optimization "ICF", which may merge different
+# functions into one if the function signature and body of them are identical.
+config("disable_icf") {
+  visibility = [ ":*" ]  # Only targets in this file can depend on this.
+  if (is_clang || use_gold) {
+    ldflags = [ "-Wl,--icf=none" ]
+  } else if (is_win) {
+    # Assume using MSVC linker
+    ldflags = [ "/OPT:NOICF" ]
+  }
+}
+
+executable("blink_v8_snapshot_generator") {
+  sources = [
+    "shell/blink_v8_snapshot_generator_main.cc",
+  ]
+
+  deps = [
+    ":gin",
+    "//mojo/edk/system:system",
+    "//third_party/WebKit/public:blink",
+    "//v8",
+  ]
+
+  # Link time optimization "ICF" breaks 1:1 mappings of the external references
+  # for V8 snapshot. So, we disable it while taking a V8 snapshot.
+  configs += [
+    "//v8:external_startup_data",
+    ":disable_icf",
+  ]
+}
+
 source_set("gin_test") {
   testonly = true
   sources = [