Support explicit pools in actions

tools/gn/variables.cc

Index: tools/gn/variables.cc
diff --git a/tools/gn/variables.cc b/tools/gn/variables.cc
index d304bc508cfef300b8b81c6378286b49caed22c9..91f1f4ee18580fbf92520271a0bb5505384843ee 100644
--- a/tools/gn/variables.cc
+++ b/tools/gn/variables.cc
@@ -1441,6 +1441,23 @@ const char kOutputs_Help[] =
     with no source expansions. See "gn help action".
 )";
 
+const char kPool[] = "pool";

[brettw, 2017/06/08 18:36:20]

This will cause a problem for help, because "gn help pool" could mean either the
variable or the target type.

We could rename the variable but most things I can think of are worse than just
"pool" (ideas?). We could potentially also special-case this in "gn help" to
have a message about how it could be a function or a variable in an action, then
print out both outputs.

+const char kPool_HelpShort[] =
+    "pool: [string] Label of the pool used by the action.";
+const char kPool_Help[] =
+    R"(pool: Label of the pool used by the action.
+
+  A fully-qualified label representing the pool that will be used for the
+  action.

[brettw, 2017/06/08 18:36:20]

Can this add "Pools are defined using the pool() {...} declaration."

[Petr Hosek, 2017/06/09 03:24:33]

Done.

+
+Example
+
+  action("action") {
+    pool = "//build:custom_pool"
+    ...
+  }
+)";
+
 const char kPrecompiledHeader[] = "precompiled_header";
 const char kPrecompiledHeader_HelpShort[] =
     "precompiled_header: [string] Header file to precompile.";