[firebase_performance] Fix invokeMethod formatting that caused a bug with Dart code obfuscation (#1874)

* Fix invokeMethod formatting that caused a bug with Dart code obfuscation
diff --git a/packages/firebase_performance/CHANGELOG.md b/packages/firebase_performance/CHANGELOG.md
index 57b64e7..f906a5d 100644
--- a/packages/firebase_performance/CHANGELOG.md
+++ b/packages/firebase_performance/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 0.3.0+3
+
+* Fix bug that caused `invokeMethod` to fail with Dart code obfuscation
+
 ## 0.3.0+2
 
 * Fix bug preventing this plugin from working with hot restart.
diff --git a/packages/firebase_performance/lib/src/firebase_performance.dart b/packages/firebase_performance/lib/src/firebase_performance.dart
index e2498ec..0ecad74 100644
--- a/packages/firebase_performance/lib/src/firebase_performance.dart
+++ b/packages/firebase_performance/lib/src/firebase_performance.dart
@@ -37,7 +37,7 @@
   /// does not reflect whether instrumentation is enabled/disabled.
   Future<bool> isPerformanceCollectionEnabled() {
     return channel.invokeMethod<bool>(
-      '$FirebasePerformance#isPerformanceCollectionEnabled',
+      'FirebasePerformance#isPerformanceCollectionEnabled',
       <String, dynamic>{'handle': _handle},
     );
   }
@@ -48,7 +48,7 @@
   /// application. By default, performance monitoring is enabled.
   Future<void> setPerformanceCollectionEnabled(bool enable) {
     return channel.invokeMethod<void>(
-      '$FirebasePerformance#setPerformanceCollectionEnabled',
+      'FirebasePerformance#setPerformanceCollectionEnabled',
       <String, dynamic>{'handle': _handle, 'enable': enable},
     );
   }
@@ -62,7 +62,7 @@
     final int handle = _nextHandle++;
 
     FirebasePerformance.channel.invokeMethod<void>(
-      '$FirebasePerformance#newTrace',
+      'FirebasePerformance#newTrace',
       <String, dynamic>{'handle': _handle, 'traceHandle': handle, 'name': name},
     );
 
@@ -74,7 +74,7 @@
     final int handle = _nextHandle++;
 
     FirebasePerformance.channel.invokeMethod<void>(
-      '$FirebasePerformance#newHttpMetric',
+      'FirebasePerformance#newHttpMetric',
       <String, dynamic>{
         'handle': _handle,
         'httpMetricHandle': handle,
diff --git a/packages/firebase_performance/lib/src/http_metric.dart b/packages/firebase_performance/lib/src/http_metric.dart
index c0b27bb..704b36c 100644
--- a/packages/firebase_performance/lib/src/http_metric.dart
+++ b/packages/firebase_performance/lib/src/http_metric.dart
@@ -59,7 +59,7 @@
 
     _httpResponseCode = httpResponseCode;
     FirebasePerformance.channel.invokeMethod<void>(
-      '$HttpMetric#httpResponseCode',
+      'HttpMetric#httpResponseCode',
       <String, dynamic>{
         'handle': _handle,
         'httpResponseCode': httpResponseCode,
@@ -76,7 +76,7 @@
 
     _requestPayloadSize = requestPayloadSize;
     FirebasePerformance.channel.invokeMethod<void>(
-      '$HttpMetric#requestPayloadSize',
+      'HttpMetric#requestPayloadSize',
       <String, dynamic>{
         'handle': _handle,
         'requestPayloadSize': requestPayloadSize,
@@ -93,7 +93,7 @@
 
     _responseContentType = responseContentType;
     FirebasePerformance.channel.invokeMethod<void>(
-      '$HttpMetric#responseContentType',
+      'HttpMetric#responseContentType',
       <String, dynamic>{
         'handle': _handle,
         'responseContentType': responseContentType,
@@ -110,7 +110,7 @@
 
     _responsePayloadSize = responsePayloadSize;
     FirebasePerformance.channel.invokeMethod<void>(
-      '$HttpMetric#responsePayloadSize',
+      'HttpMetric#responsePayloadSize',
       <String, dynamic>{
         'handle': _handle,
         'responsePayloadSize': responsePayloadSize,
@@ -129,7 +129,7 @@
 
     _hasStarted = true;
     return FirebasePerformance.channel.invokeMethod<void>(
-      '$HttpMetric#start',
+      'HttpMetric#start',
       <String, dynamic>{'handle': _handle},
     );
   }
@@ -147,7 +147,7 @@
 
     _hasStopped = true;
     return FirebasePerformance.channel.invokeMethod<void>(
-      '$HttpMetric#stop',
+      'HttpMetric#stop',
       <String, dynamic>{'handle': _handle},
     );
   }
diff --git a/packages/firebase_performance/lib/src/performance_attributes.dart b/packages/firebase_performance/lib/src/performance_attributes.dart
index 77d4f18..020b61a 100644
--- a/packages/firebase_performance/lib/src/performance_attributes.dart
+++ b/packages/firebase_performance/lib/src/performance_attributes.dart
@@ -48,7 +48,7 @@
 
     _attributes[name] = value;
     return FirebasePerformance.channel.invokeMethod<void>(
-      '$PerformanceAttributes#putAttribute',
+      'PerformanceAttributes#putAttribute',
       <String, dynamic>{
         'handle': _handle,
         'name': name,
@@ -66,7 +66,7 @@
 
     _attributes.remove(name);
     return FirebasePerformance.channel.invokeMethod<void>(
-      '$PerformanceAttributes#removeAttribute',
+      'PerformanceAttributes#removeAttribute',
       <String, dynamic>{'handle': _handle, 'name': name},
     );
   }
@@ -85,7 +85,7 @@
     }
 
     return FirebasePerformance.channel.invokeMapMethod<String, String>(
-      '$PerformanceAttributes#getAttributes',
+      'PerformanceAttributes#getAttributes',
       <String, dynamic>{'handle': _handle},
     );
   }
diff --git a/packages/firebase_performance/lib/src/trace.dart b/packages/firebase_performance/lib/src/trace.dart
index cf8e1fb..43efb25 100644
--- a/packages/firebase_performance/lib/src/trace.dart
+++ b/packages/firebase_performance/lib/src/trace.dart
@@ -52,7 +52,7 @@
 
     _hasStarted = true;
     return FirebasePerformance.channel.invokeMethod<void>(
-      '$Trace#start',
+      'Trace#start',
       <String, dynamic>{'handle': _handle},
     );
   }
@@ -70,7 +70,7 @@
 
     _hasStopped = true;
     return FirebasePerformance.channel.invokeMethod<void>(
-      '$Trace#stop',
+      'Trace#stop',
       <String, dynamic>{'handle': _handle},
     );
   }
@@ -88,7 +88,7 @@
     _metrics.putIfAbsent(name, () => 0);
     _metrics[name] += value;
     return FirebasePerformance.channel.invokeMethod<void>(
-      '$Trace#incrementMetric',
+      'Trace#incrementMetric',
       <String, dynamic>{'handle': _handle, 'name': name, 'value': value},
     );
   }
@@ -103,7 +103,7 @@
 
     _metrics[name] = value;
     return FirebasePerformance.channel.invokeMethod<void>(
-      '$Trace#setMetric',
+      'Trace#setMetric',
       <String, dynamic>{'handle': _handle, 'name': name, 'value': value},
     );
   }
@@ -116,7 +116,7 @@
     if (_hasStopped) return Future<int>.value(_metrics[name] ?? 0);
 
     return FirebasePerformance.channel.invokeMethod<int>(
-      '$Trace#getMetric',
+      'Trace#getMetric',
       <String, dynamic>{'handle': _handle, 'name': name},
     );
   }
diff --git a/packages/firebase_performance/pubspec.yaml b/packages/firebase_performance/pubspec.yaml
index 0a8f3bd..01ab9f3 100644
--- a/packages/firebase_performance/pubspec.yaml
+++ b/packages/firebase_performance/pubspec.yaml
@@ -4,7 +4,7 @@
   iOS.
 author: Flutter Team <flutter-dev@googlegroups.com>
 homepage: https://github.com/flutter/plugins/tree/master/packages/firebase_performance
-version: 0.3.0+2
+version: 0.3.0+3
 
 dependencies:
   flutter: