Filter Android logs by the pid of the remote process (#9293)

Fixes https://github.com/flutter/flutter/issues/6849

packages/flutter_tools/lib/src/vmservice.dart

diff --git a/packages/flutter_tools/lib/src/vmservice.dart b/packages/flutter_tools/lib/src/vmservice.dart
index d9afbfd..7b9f1ac 100644
--- a/packages/flutter_tools/lib/src/vmservice.dart
+++ b/packages/flutter_tools/lib/src/vmservice.dart
@@ -507,6 +507,7 @@
     _loaded = true;
 
     // TODO(johnmccutchan): Extract any properties we care about here.
+    _pid = map['pid'];
 
     // Remove any isolates which are now dead from the isolate cache.
     _removeDeadIsolates(map['isolates']);
@@ -521,6 +522,11 @@
   /// The set of live views.
   final Map<String, FlutterView> _viewCache = <String, FlutterView>{};
 
+  /// The pid of the VM's process.
+  int _pid;
+
+  int get pid => _pid;
+
   int _compareIsolates(Isolate a, Isolate b) {
     final DateTime aStart = a.startTime;
     final DateTime bStart = b.startTime;