Add support for user defined "pool" to GN.

tools/gn/ninja_toolchain_writer.cc

Index: tools/gn/ninja_toolchain_writer.cc
diff --git a/tools/gn/ninja_toolchain_writer.cc b/tools/gn/ninja_toolchain_writer.cc
index e7459ebb3cfa2ede1e0d5303aedfdf0b36e134b2..0e6beedcbf98214f480ebe01de2fe80bd5026d71 100644
--- a/tools/gn/ninja_toolchain_writer.cc
+++ b/tools/gn/ninja_toolchain_writer.cc
@@ -11,6 +11,7 @@
 #include "tools/gn/build_settings.h"
 #include "tools/gn/filesystem_utils.h"
 #include "tools/gn/ninja_utils.h"
+#include "tools/gn/pool.h"
 #include "tools/gn/settings.h"
 #include "tools/gn/substitution_writer.h"
 #include "tools/gn/target.h"
@@ -70,6 +71,22 @@ bool NinjaToolchainWriter::RunAndWriteFile(
 void NinjaToolchainWriter::WriteRules() {
   std::string rule_prefix = GetNinjaRulePrefixForToolchain(settings_);
 
+  UniqueVector<const Pool*> pools;
+  for (int i = Toolchain::TYPE_NONE + 1; i < Toolchain::TYPE_NUMTYPES; i++) {
+    Toolchain::ToolType tool_type = static_cast<Toolchain::ToolType>(i);
+    const Tool* tool = toolchain_->GetTool(tool_type);
+    if (tool && tool->pool_label_pair().ptr)
+      pools.push_back(tool->pool_label_pair().ptr);
+  }
+
+  if (!pools.empty()) {
+    for (const Pool* pool : pools) {
+      out_ << "pool " << rule_prefix << pool->label().name() << std::endl;

[brettw, 2016/05/24 22:03:31]

How the naming works here is a bit suspicious.

In the build files, a pool is identified by a label, but then only the past part
of that label is used for the actual pool name, so it must be globally unique.
Nothing else works this way. I think we should generate a name we give to Ninja
for the pool that's based on the full label name. Probably this name should also
include the toolchain of the pool (see my other comment in the documentation).

[sdefresne, 2016/05/26 15:38:37]

Done.

+      out_ << kIndent << "depth = " << pool->depth() << std::endl;
+    }
+    out_ << std::endl;
+  }
+
   for (int i = Toolchain::TYPE_NONE + 1; i < Toolchain::TYPE_NUMTYPES; i++) {
     Toolchain::ToolType tool_type = static_cast<Toolchain::ToolType>(i);
     const Tool* tool = toolchain_->GetTool(tool_type);
@@ -117,6 +134,11 @@ void NinjaToolchainWriter::WriteToolRule(const Toolchain::ToolType type,
 
   if (tool->restat())
     out_ << kIndent << "restat = 1" << std::endl;
+
+  if (tool->pool_label_pair().ptr) {
+    out_ << kIndent << "pool = "
+         << rule_prefix << tool->pool_label_pair().label.name() << std::endl;
+  }
 }
 
 void NinjaToolchainWriter::WriteRulePattern(const char* name,