Reland of land "Turn libbase into a component"

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index e736f99430356e0696442d7ae2c7e69cc396df93..0ee906c8c342241a9ac65d0a2de78d022be3a388 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -130,6 +130,17 @@
   include_dirs = [ "include" ]
 }
 
+# This config should be applied to code using the libbase.
+config("libbase_config") {
+  if (is_component_build) {
+    defines = [ "USING_V8_BASE_SHARED" ]
+  }
+  libs = []
+  if (is_android && current_toolchain != host_toolchain) {
+    libs += [ "log" ]
+  }
+}
+
 # This config should be applied to code using the libsampler.
 config("libsampler_config") {
   include_dirs = [ "include" ]
@@ -144,10 +155,6 @@
   include_dirs = [ "include" ]
   if (v8_enable_inspector_override) {
     include_dirs += [ "$target_gen_dir/include" ]
-  }
-  libs = []
-  if (is_android && current_toolchain != host_toolchain) {
-    libs += [ "log" ]
   }
 }
 
@@ -2150,9 +2157,7 @@
   }
 }
 
-v8_source_set("v8_libbase") {
-  visibility = [ ":*" ]  # Only targets in this file can depend on this.
-
+v8_component("v8_libbase") {
   sources = [
     "src/base/adapters.h",
     "src/base/atomic-utils.h",
@@ -2168,6 +2173,7 @@
     "src/base/atomicops_internals_x86_gcc.cc",
     "src/base/atomicops_internals_x86_gcc.h",
     "src/base/atomicops_internals_x86_msvc.h",
+    "src/base/base-export.h",
     "src/base/bits.cc",
     "src/base/bits.h",
     "src/base/build_config.h",
@@ -2218,7 +2224,13 @@
 
   configs = [ ":internal_config_base" ]
 
+  public_configs = [ ":libbase_config" ]
+
   defines = []
+
+  if (is_component_build) {
+    defines = [ "BUILDING_V8_BASE_SHARED" ]
+  }
 
   if (is_posix) {
     sources += [ "src/base/platform/platform-posix.cc" ]
@@ -2363,6 +2375,7 @@
   ]
 
   public_deps = [
+    ":v8_libbase",
     ":v8_libplatform",
   ]
 }
@@ -2391,6 +2404,7 @@
 
     deps = [
       ":v8_base",
+      ":v8_libbase",
       ":v8_libplatform",
       ":v8_nosnapshot",
       "//build/config/sanitizers:deps",
@@ -2513,6 +2527,7 @@
   deps = [
     ":d8_js2c",
     ":v8",
+    ":v8_libbase",
     ":v8_libplatform",
     "//build/config/sanitizers:deps",
     "//build/win:default_exe_manifest",
@@ -2553,6 +2568,7 @@
 
   deps = [
     ":v8",
+    ":v8_libbase",
     ":v8_libplatform",
     "//build/config/sanitizers:deps",
     "//build/win:default_exe_manifest",
@@ -2577,6 +2593,7 @@
 
   deps = [
     ":v8",
+    ":v8_libbase",
     ":v8_libplatform",
     "//build/config/sanitizers:deps",
     "//build/win:default_exe_manifest",
@@ -2599,6 +2616,7 @@
   ]
 
   deps = [
+    ":v8_libbase",
     ":v8_libplatform",
     "//build/config/sanitizers:deps",
     "//build/win:default_exe_manifest",
@@ -2642,6 +2660,7 @@
 
     deps = [
       ":v8",
+      ":v8_libbase",
       ":v8_libplatform",
       "//build/config/sanitizers:deps",
       "//build/win:default_exe_manifest",