Use absolute paths as canonical paths for inputs digest maps

Change-Id: I9a6c5efe22d4ef1f46393e2983084fe0b8a4652b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/107682
Reviewed-by: David Morgan <davidmorgan@google.com>
Reviewed-by: Jens Johansen <jensj@google.com>
Commit-Queue: Jake Macdonald <jakemac@google.com>

pkg/dev_compiler/bin/dartdevc.dart

@@ -56,11 +56,7 @@ class _CompilerWorker extends AsyncWorkerLoop {
     /// Build a map of uris to digests.
     final inputDigests = <Uri, List<int>>{};
     for (var input in request.inputs) {
-      var uri = Uri.parse(input.path);
-      if (uri.scheme.isEmpty) {
-        uri = Uri.parse('file://${input.path}');
-      }
-      inputDigests[uri] = input.digest;
+      inputDigests[Uri.base.resolve(input.path)] = input.digest;
     }
 
     lastResult = await runZoned(

utils/bazel/kernel_worker.dart

@@ -250,11 +250,7 @@ Future<ComputeKernelResult> computeKernel(List<String> args,
     /// Build a map of uris to digests.
     final inputDigests = <Uri, List<int>>{};
     for (var input in inputs) {
-      var uri = Uri.parse(input.path);
-      if (uri.scheme.isEmpty) {
-        uri = Uri.parse('file://${input.path}');
-      }
-      inputDigests[uri] = input.digest;
+      inputDigests[_toUri(input.path)] = input.digest;
     }
 
     // TODO(sigmund): add support for experiments with the incremental compiler.