[gn] Add unittests

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index 82023a4add3362f46abc61738c6608a66fc35ca9..13940c01ade4305abb7a678978209775d92e146e 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -69,15 +69,6 @@ declare_args() {
 v8_random_seed = "314159265"
 v8_toolset_for_shell = "host"
 
-if (v8_use_snapshot && v8_use_external_startup_data) {
-  snapshot_target = ":v8_external_snapshot"
-} else if (v8_use_snapshot) {
-  snapshot_target = ":v8_snapshot"
-} else {
-  assert(!v8_use_external_startup_data)
-  snapshot_target = ":v8_nosnapshot"
-}
-
 ###############################################################################
 # Configurations
 #
@@ -643,6 +634,17 @@ action("run_mksnapshot") {
 # Source Sets (aka static libraries)
 #
 
+source_set("v8_maybe_snapshot") {
+  if (v8_use_snapshot && v8_use_external_startup_data) {
+    public_deps = [ ":v8_external_snapshot" ]
+  } else if (v8_use_snapshot) {
+    public_deps = [ ":v8_snapshot" ]
+  } else {
+    assert(!v8_use_external_startup_data)
+    public_deps = [ ":v8_nosnapshot" ]
+  }
+}
+
 v8_source_set("v8_nosnapshot") {
   visibility = [ ":*" ]  # Only targets in this file can depend on this.
 
@@ -2002,7 +2004,7 @@ v8_source_set("fuzzer_support") {
   configs = [ ":internal_config_base" ]
 
   deps = [
-    snapshot_target,
+    ":v8_maybe_snapshot",
   ]
 
   public_deps = [
@@ -2044,6 +2046,33 @@ if (current_toolchain == v8_snapshot_toolchain) {
 # Public targets
 #
 
+want_v8_shell = (
+    (current_toolchain == host_toolchain && v8_toolset_for_shell == "host") ||
+    (current_toolchain == v8_snapshot_toolchain &&
+     v8_toolset_for_shell == "host") ||
+    (current_toolchain != host_toolchain && v8_toolset_for_shell == "target"))
+
+group("gn_all") {
+  testonly = true
+
+  deps = [
+    ":d8",
+  ]
+
+  if (want_v8_shell) {
+    deps += [
+      ":v8_shell",
+    ]
+  }
+
+  if (host_os != "mac" || !is_android) {
+    # These items don't compile for Android on Mac.
+    deps += [
+      "test/unittests:unittests",
+    ]
+  }
+}
+
 if (is_component_build) {
   component("v8") {
     sources = [
@@ -2052,7 +2081,7 @@ if (is_component_build) {
 
     public_deps = [
       ":v8_base",
-      snapshot_target,
+      ":v8_maybe_snapshot",
     ]
 
     configs -= [ "//build/config/compiler:chromium_code" ]
@@ -2069,7 +2098,7 @@ if (is_component_build) {
   group("v8") {
     public_deps = [
       ":v8_base",
-      snapshot_target,
+      ":v8_maybe_snapshot",
     ]
     public_configs = [ ":external_config" ]
   }
@@ -2116,10 +2145,7 @@ executable("d8") {
   }
 }
 
-if ((current_toolchain == host_toolchain && v8_toolset_for_shell == "host") ||
-    (current_toolchain == v8_snapshot_toolchain &&
-     v8_toolset_for_shell == "host") ||
-    (current_toolchain != host_toolchain && v8_toolset_for_shell == "target")) {
+if (want_v8_shell) {
   executable("v8_shell") {
     sources = [
       "samples/shell.cc",