[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 f386fb6b22253fc5d1befbfdb564a22036d67ec6..87cc3a5e69183a5537e9f4fe7b677a193b71743f 100644
--- a/gin/BUILD.gn
+++ b/gin/BUILD.gn
@@ -95,11 +95,11 @@ component("gin") {
   }
 
   defines = [ "GIN_IMPLEMENTATION" ]
-
   public_deps = [
     "//base",
     "//v8",
   ]
+
   deps = [
     ":gin_features",
     "//base/third_party/dynamic_annotations",
@@ -130,6 +130,62 @@ executable("gin_shell") {
   configs += [ "//v8:external_startup_data" ]
 }
 
+group("v8_context_snapshot_for_blink") {
+  public_deps = [
+    ":generate_v8_context_snapshot_for_blink",
+  ]
+}
+
+action("generate_v8_context_snapshot_for_blink") {
+  script = "run.py"
+  output_file = "$root_out_dir/context_blob.bin"
+  output_path = rebase_path(output_file, root_build_dir)
+
+  args = [
+    "./" + rebase_path(get_label_info(":gin_blink_snapshot($host_toolchain)",
+                                      "root_out_dir") + "/gin_blink_snapshot",
+                       root_build_dir),
+    "--output_file=$output_path",
+  ]
+
+  outputs = [
+    output_file,
+  ]
+
+  deps = [
+    ":gin_blink_snapshot($host_toolchain)",
+  ]
+}
+
+# This config disables a link time optimization which merge some pointers,
+# but we must keep duplicated entries in external references for V8 snapshot.

[Yuki, 2017/05/30 14:35:56]

Good comment.  Let's make this a little more explicit.  The following is just an
example.

This config disables a link time optimization, which may merge two different
functions into one if the function signature and body of them are identical. 
This unification breaks 1:1 mappings of the external references of V8 snapshot. 
So, disables the LTO while taking a V8 snapshot.

[peria, 2017/06/01 08:33:32]

Done.

+config("disable_icf") {
+  visibility = [ ":*" ]  # Only targets in this file can depend on this.
+  if (is_win) {
+    ldflags = [ "/OPT:NOICF" ]
+  } else if (is_posix && !is_mac) {
+    ldflags = [ "-Wl,--icf=none" ]
+  }
+}
+
+executable("gin_blink_snapshot") {

[Yuki, 2017/05/30 14:35:56]

nit: s/gin_blink_snapshot/gin_blink_v8_snapshot/

[peria, 2017/06/01 08:33:32]

Done.

+  sources = [
+    "shell/gin_prepare_main.cc",
+  ]
+
+  deps = [
+    ":gin",
+    "//mojo/edk/system:system",
+    "//third_party/WebKit/public:blink",
+    "//v8",
+  ]
+
+  configs += [
+    "//v8:external_startup_data",
+    ":disable_icf",
+  ]
+}
+
 source_set("gin_test") {
   testonly = true
   sources = [