Support more configurability in GN toolchains

tools/gn/substitution_pattern.h

Index: tools/gn/substitution_pattern.h
diff --git a/tools/gn/substitution_pattern.h b/tools/gn/substitution_pattern.h
index 70fc5eb375a00e4fcc909feaa0d648c9a62e7ea9..7e6c662519ad4518b25961480f1d298418e036ae 100644
--- a/tools/gn/substitution_pattern.h
+++ b/tools/gn/substitution_pattern.h
@@ -10,6 +10,7 @@
 
 #include "tools/gn/substitution_type.h"
 
+class BuildSettings;
 class Err;
 class ParseNode;
 class Value;
@@ -22,6 +23,10 @@ class SubstitutionPattern {
     Subrange(SubstitutionType t, const std::string& l = std::string());
     ~Subrange();
 
+    inline bool operator==(const Subrange& other) const {
+      return type == other.type && literal == other.literal;
+    }
+
     SubstitutionType type;
 
     // When type_ == LITERAL, this specifies the literal.
@@ -41,7 +46,13 @@ class SubstitutionPattern {
 
   // Sets the bits in the given vector corresponding to the substitutions used
   // by this pattern. SUBSTITUTION_LITERAL is ignored.
-  void FillRequiredTypes(bool required_types[SUBSTITUTION_NUM_TYPES]) const;
+  void FillRequiredTypes(SubstitutionBits* bits) const;
+
+  // Checks whether this pattern resolves to something in the output directory
+  // for the given build settings. If not, returns false and fills in the given
+  // error.
+  bool IsInOutputDir(const BuildSettings* build_settings,
+                     Err* err) const;
 
   // Returns a vector listing the substitutions used by this pattern, not
   // counting SUBSTITUTION_LITERAL.
@@ -54,6 +65,7 @@ class SubstitutionPattern {
 
  private:
   std::vector<Subrange> ranges_;
+  const ParseNode* origin_;
 
   std::vector<SubstitutionType> required_types_;
 };