Add initial prototype for the GN meta-buildsystem.

tools/gn/target_manager.h

Index: tools/gn/target_manager.h
diff --git a/tools/gn/target_manager.h b/tools/gn/target_manager.h
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+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef TOOLS_GN_TARGET_MANAGER_H_
+#define TOOLS_GN_TARGET_MANAGER_H_
+
+#include <set>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/containers/hash_tables.h"
+#include "base/synchronization/lock.h"
+#include "tools/gn/target.h"
+
+class BuildSettings;
+class Err;
+class ItemTree;
+class LocationRange;
+class ToolchainManager;
+class Value;
+
+// Manages all the targets in the system. This integrates with the ItemTree
+// to manage the target-specific rules and creation.
+//
+// This class is threadsafe.
+class TargetManager {
+ public:
+  explicit TargetManager(const BuildSettings* settings);
+  ~TargetManager();
+
+  // Gets a reference to a named target. The given target name is created if
+  // it doesn't exist.
+  //
+  // The label should be fully specified in that it should include an
+  // explicit toolchain.
+  //
+  // |specified_from_here| should indicate the dependency or the target
+  // generator causing this access for error message generation.
+  //
+  // |dep_from| should be set when a target is getting a dep that it depends
+  // on. |dep_from| indicates the target that specified the dependency. It
+  // will be used to track outstanding dependencies so we can know when the
+  // target and all of its dependencies are complete. It should be null when
+  // getting a target for other reasons.
+  //
+  // On failure, |err| will be set.
+  //
+  // The returned pointer must not be dereferenced until it's generated, since
+  // it could be being generated on another thread.
+  Target* GetTarget(const Label& label,
+                    const LocationRange& specified_from_here,
+                    Target* dep_from,
+                    Err* err);
+
+  // Called by a target when it has been loaded from the .gin file. Its
+  // dependencies may or may not be resolved yet.
+  void TargetGenerationComplete(const Label& label);
+
+  // Returns a list of all targets.
+  void GetAllTargets(std::vector<const Target*>* all_targets) const;
+
+ private:
+  bool ScheduleInvocationLocked(const LocationRange& specified_from_here,
+                                const Label& label,
+                                Err* err);
+
+  const BuildSettings* build_settings_;
+
+  DISALLOW_COPY_AND_ASSIGN(TargetManager);
+};
+
+#endif  // TOOLS_GN_TARGET_MANAGER_H