Turn libplatform into a component

BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/android/config.gni")
 import("//build/config/arm.gni")
 import("//build/config/dcheck_always_on.gni")
 import("//build/config/mips.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 
@@ skipping 110 matching lines @@
 
 config("internal_config_base") {
   visibility = [ ":*" ]  # Only targets in this file can depend on this.
 
   include_dirs = [ "." ]
 }
 
 # This config should be applied to code using the libplatform.
 config("libplatform_config") {
   include_dirs = [ "include" ]
+  if (is_component_build) {
+    defines = [ "USING_V8_PLATFORM_SHARED" ]
+  }
 }
 
 # This config should be applied to code using the libsampler.
 config("libsampler_config") {
   include_dirs = [ "include" ]
 }
 
 # This config should only be applied to code using V8 and not any V8 code
 # itself.
 config("external_config") {
@@ skipping 2132 matching lines @@
       "dbghelp.lib",
       "shlwapi.lib",
       "winmm.lib",
       "ws2_32.lib",
     ]
   }
 
   # TODO(jochen): Add support for qnx, freebsd, openbsd, netbsd, and solaris.
 }
 
-v8_source_set("v8_libplatform") {
+v8_component("v8_libplatform") {
   sources = [
     "//base/trace_event/common/trace_event_common.h",
+    "include/libplatform/libplatform-export.h",
     "include/libplatform/libplatform.h",
     "include/libplatform/v8-tracing.h",
     "src/libplatform/default-platform.cc",
     "src/libplatform/default-platform.h",
     "src/libplatform/task-queue.cc",
     "src/libplatform/task-queue.h",
     "src/libplatform/tracing/trace-buffer.cc",
     "src/libplatform/tracing/trace-buffer.h",
     "src/libplatform/tracing/trace-config.cc",
     "src/libplatform/tracing/trace-object.cc",
     "src/libplatform/tracing/trace-writer.cc",
     "src/libplatform/tracing/trace-writer.h",
     "src/libplatform/tracing/tracing-controller.cc",
     "src/libplatform/worker-thread.cc",
     "src/libplatform/worker-thread.h",
   ]
 
   configs = [ ":internal_config_base" ]
 
+  if (is_component_build) {
+    defines = [ "BUILDING_V8_PLATFORM_SHARED" ]
+  }
+
   public_configs = [ ":libplatform_config" ]
 
   deps = [
     ":v8_libbase",
   ]
 }
 
 v8_source_set("v8_libsampler") {
   sources = [
     "src/libsampler/sampler.cc",
@@ skipping 616 matching lines @@
   ]
 
   configs = [
     ":external_config",
     ":internal_config_base",
   ]
 }
 
 v8_fuzzer("wasm_data_section_fuzzer") {
 }