Support explicit pools in actions

tools/gn/loader.cc

Index: tools/gn/loader.cc
diff --git a/tools/gn/loader.cc b/tools/gn/loader.cc
index 0ede3c95548389882fab5481a9f3ad532cb5e061..741b7e6bd2070629b2283a6f32500f6de0a040b2 100644
--- a/tools/gn/loader.cc
+++ b/tools/gn/loader.cc
@@ -10,14 +10,17 @@
 #include "tools/gn/build_settings.h"
 #include "tools/gn/err.h"
 #include "tools/gn/filesystem_utils.h"
+#include "tools/gn/functions.h"
 #include "tools/gn/input_file_manager.h"
 #include "tools/gn/parse_tree.h"
+#include "tools/gn/pool.h"
 #include "tools/gn/scheduler.h"
 #include "tools/gn/scope_per_file_provider.h"
 #include "tools/gn/settings.h"
 #include "tools/gn/source_dir.h"
 #include "tools/gn/source_file.h"
 #include "tools/gn/trace.h"
+#include "tools/gn/variables.h"
 
 namespace {
 
@@ -339,6 +342,14 @@ void LoaderImpl::BackgroundLoadBuildConfig(
     }
   }
 
+  // Create the predefined console pool object.

[brettw, 2017/06/28 21:23:27]

This seems weird to me. It looks like this will be creating a pool in Chrome
named "//build/config:console". I don't know how one is supposed to know about
this.

From what Opera said we don't need this. Let's just delete the console support.
If we need console pools, I'd rather add a "console" variable to the pool
definition and map anything with this flag to the builtin one.

[Petr Hosek, 2017/06/28 23:42:32]

It has "//:console" label but it's accessible through a prebuilt console
variable, similarly to e.g. current_os or current_cpu, so you can do pool =
console. I agree that it's probably easier to remove this altogether if it's no
longer needed.

+  Label label(MakeLabelForScope(base_config, nullptr, "console"));
+  std::unique_ptr<Pool> pool(new Pool(base_config->settings(), label));
+  pool->set_console(true);
+  Value console_val(nullptr, label.GetUserVisibleName(true));
+  base_config->SetValue(variables::kConsole, console_val, nullptr);
+  settings->build_settings()->ItemDefined(std::move(pool));
+
   task_runner_->PostTask(FROM_HERE,
                          base::Bind(&LoaderImpl::DidLoadBuildConfig, this,
                                     settings->toolchain_label()));