Add support for reading .gypi files.

tools/gn/input_file_manager.cc

Index: tools/gn/input_file_manager.cc
diff --git a/tools/gn/input_file_manager.cc b/tools/gn/input_file_manager.cc
index 0c4bf280c408a2722e6145d821d2e57da42de6d8..ddd79596341cafee67e9bae961427c26d88f5377 100644
--- a/tools/gn/input_file_manager.cc
+++ b/tools/gn/input_file_manager.cc
@@ -38,6 +38,7 @@ InputFileManager::~InputFileManager() {
   // Should be single-threaded by now.
   STLDeleteContainerPairSecondPointers(input_files_.begin(),
                                        input_files_.end());
+  STLDeleteContainerPointers(dynamic_inputs_.begin(), dynamic_inputs_.end());
 }
 
 bool InputFileManager::AsyncLoadFile(const LocationRange& origin,
@@ -166,6 +167,19 @@ const ParseNode* InputFileManager::SyncLoadFile(
   return data->parsed_root.get();
 }
 
+void InputFileManager::AddDynamicInput(InputFile** file,
+                                       std::vector<Token>** tokens,
+                                       scoped_ptr<ParseNode>** parse_root) {
+  InputFileData* data = new InputFileData(SourceFile());
+  {
+    base::AutoLock lock(lock_);
+    dynamic_inputs_.push_back(data);
+  }
+  *file = &data->file;
+  *tokens = &data->tokens;
+  *parse_root = &data->parsed_root;
+}
+
 int InputFileManager::GetInputFileCount() const {
   base::AutoLock lock(lock_);
   return static_cast<int>(input_files_.size());