Add support for user defined "pool" to GN.

tools/gn/builder.cc

Index: tools/gn/builder.cc
diff --git a/tools/gn/builder.cc b/tools/gn/builder.cc
index 22b4c478c9bd347ded71d84ad6b14469df99cf22..036d3902c707ff2e183059d94bd223553d8866b8 100644
--- a/tools/gn/builder.cc
+++ b/tools/gn/builder.cc
@@ -11,6 +11,7 @@
 #include "tools/gn/deps_iterator.h"
 #include "tools/gn/err.h"
 #include "tools/gn/loader.h"
+#include "tools/gn/pool.h"
 #include "tools/gn/scheduler.h"
 #include "tools/gn/settings.h"
 #include "tools/gn/target.h"
@@ -263,6 +264,19 @@ bool Builder::ToolchainDefined(BuilderRecord* record, Err* err) {
   if (!AddDeps(record, toolchain->deps(), err))
     return false;
 
+  for (int i = Toolchain::TYPE_NONE + 1; i < Toolchain::TYPE_NUMTYPES; i++) {
+    Toolchain::ToolType tool_type = static_cast<Toolchain::ToolType>(i);
+    Tool* tool = toolchain->GetTool(tool_type);
+    if (!tool || tool->pool().label.is_null())
+      continue;
+
+    BuilderRecord* dep_record = GetOrCreateRecordOfType(
+        tool->pool().label, tool->pool().origin, BuilderRecord::ITEM_POOL, err);
+    if (!dep_record)
+      return false;
+    record->AddDep(dep_record);
+  }
+
   // The default toolchain gets generated by default. Also propogate the
   // generate flag if it depends on items in a non-default toolchain.
   if (record->should_generate() ||
@@ -429,6 +443,8 @@ bool Builder::ResolveItem(BuilderRecord* record, Err* err) {
     Toolchain* toolchain = record->item()->AsToolchain();
     if (!ResolveDeps(&toolchain->deps(), err))
       return false;
+    if (!ResolvePools(toolchain, err))
+      return false;
   }
 
   record->set_resolved(true);
@@ -497,6 +513,29 @@ bool Builder::ResolveToolchain(Target* target, Err* err) {
   return true;
 }
 
+bool Builder::ResolvePools(Toolchain* toolchain, Err* err) {
+  for (int i = Toolchain::TYPE_NONE + 1; i < Toolchain::TYPE_NUMTYPES; i++) {
+    Toolchain::ToolType tool_type = static_cast<Toolchain::ToolType>(i);
+    Tool* tool = toolchain->GetTool(tool_type);
+    if (!tool || tool->pool().label.is_null())
+      continue;
+
+    BuilderRecord* record =
+        GetResolvedRecordOfType(tool->pool().label, toolchain->defined_from(),
+                                BuilderRecord::ITEM_POOL, err);
+    if (!record) {
+      *err = Err(tool->pool().origin, "Pool for tool not defined.",
+                 "I was hoping to find a pool " +
+                     tool->pool().label.GetUserVisibleName(false));
+      return false;
+    }
+
+    tool->set_pool(LabelPtrPair<Pool>(record->item()->AsPool()));
+  }
+
+  return true;
+}
+
 std::string Builder::CheckForCircularDependencies(
     const std::vector<const BuilderRecord*>& bad_records) const {
   std::vector<const BuilderRecord*> cycle;