Implement tracking of BUILD.gn files used to define target, toolchain or

tools/gn/scope.cc

Index: tools/gn/scope.cc
diff --git a/tools/gn/scope.cc b/tools/gn/scope.cc
index f2fe7521dfafc8e94f5a6c35ff2723a9ec960c9f..8158e82ccc6cef91223d9a34749733ddf39c6b67 100644
--- a/tools/gn/scope.cc
+++ b/tools/gn/scope.cc
@@ -7,6 +7,7 @@
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "tools/gn/parse_tree.h"
+#include "tools/gn/source_file.h"
 #include "tools/gn/template.h"
 
 namespace {
@@ -39,29 +40,30 @@ Scope::ProgrammaticProvider::~ProgrammaticProvider() {
   scope_->RemoveProvider(this);
 }
 
-Scope::Scope(const Settings* settings)
+Scope::Scope(const Settings* settings,
+             const std::set<uint32_t>& source_files_hashes)
     : const_containing_(nullptr),
       mutable_containing_(nullptr),
       settings_(settings),
       mode_flags_(0),
-      item_collector_(nullptr) {
-}
+      item_collector_(nullptr),
+      source_files_hashes_(source_files_hashes) {}
 
 Scope::Scope(Scope* parent)
     : const_containing_(nullptr),
       mutable_containing_(parent),
       settings_(parent->settings()),
       mode_flags_(0),
-      item_collector_(nullptr) {
-}
+      item_collector_(nullptr),
+      source_files_hashes_(parent->source_files_hashes_) {}
 
 Scope::Scope(const Scope* parent)
     : const_containing_(parent),
       mutable_containing_(nullptr),
       settings_(parent->settings()),
       mode_flags_(0),
-      item_collector_(nullptr) {
-}
+      item_collector_(nullptr),
+      source_files_hashes_(parent->source_files_hashes_) {}
 
 Scope::~Scope() {
 }
@@ -339,7 +341,7 @@ bool Scope::NonRecursiveMergeTo(Scope* dest,
     }
 
     std::unique_ptr<Scope>& dest_scope = dest->target_defaults_[current_name];
-    dest_scope = base::MakeUnique<Scope>(settings_);
+    dest_scope = base::MakeUnique<Scope>(settings_, source_files_hashes_);
     pair.second->NonRecursiveMergeTo(dest_scope.get(), options, node_for_err,
                                      "<SHOULDN'T HAPPEN>", err);
   }
@@ -397,6 +399,10 @@ bool Scope::NonRecursiveMergeTo(Scope* dest,
     dest->templates_[current_name] = pair.second;
   }
 
+  // Source files.
+  dest->source_files_hashes_.insert(source_files_hashes_.begin(),
+                                    source_files_hashes_.end());
+
   return true;
 }
 
@@ -412,7 +418,7 @@ std::unique_ptr<Scope> Scope::MakeClosure() const {
     result = mutable_containing_->MakeClosure();
   } else {
     // This is a standalone scope, just copy it.
-    result.reset(new Scope(settings_));
+    result.reset(new Scope(settings_, source_files_hashes_));
   }
 
   // Want to clobber since we've flattened some nested scopes, and our parent
@@ -430,7 +436,7 @@ std::unique_ptr<Scope> Scope::MakeClosure() const {
 
 Scope* Scope::MakeTargetDefaults(const std::string& target_type) {
   std::unique_ptr<Scope>& dest = target_defaults_[target_type];
-  dest = base::MakeUnique<Scope>(settings_);
+  dest = base::MakeUnique<Scope>(settings_, source_files_hashes_);
   return dest.get();
 }
 
@@ -495,6 +501,10 @@ const SourceDir& Scope::GetSourceDir() const {
   return source_dir_;
 }
 
+void Scope::AddSourceFile(const SourceFile& source_file) {
+  source_files_hashes_.insert(base::Hash(source_file.value()));
+}
+
 Scope::ItemVector* Scope::GetItemCollector() {
   if (item_collector_)
     return item_collector_;