Document service lifetime

Author: jansvoboda11

clang/include/clang/Tooling/DependencyScanning/DependencyScanningTool.h

@@ -79,6 +79,9 @@ struct P1689Rule {
 class DependencyScanningTool {
 public:
   /// Construct a dependency scanning tool.
+  ///
+  /// @param Service  The parent service. Must outlive the tool.
+  /// @param FS The filesystem for the tool to use. Defaults to the physical FS.
   DependencyScanningTool(DependencyScanningService &Service,
                          llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS =
                              llvm::vfs::createPhysicalFileSystem());

clang/include/clang/Tooling/DependencyScanning/DependencyScanningWorker.h

@@ -80,6 +80,10 @@ class DependencyActionController {
 /// using the regular processing run.
 class DependencyScanningWorker {
 public:
+  /// Construct a dependency scanning worker.
+  ///
+  /// @param Service The parent service. Must outlive the worker.
+  /// @param FS The filesystem for the worker to use.
   DependencyScanningWorker(DependencyScanningService &Service,
                            llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS);