Perform a full GC by default when requesting a heap snapshot.

runtime/observatory/lib/src/app/location_manager.dart

Index: runtime/observatory/lib/src/app/location_manager.dart
diff --git a/runtime/observatory/lib/src/app/location_manager.dart b/runtime/observatory/lib/src/app/location_manager.dart
index fee288446c94b6efc7629d4b576c0ba3367e3faa..577cb92101c87337cbe476abbe33c5d1d6c6dc25 100644
--- a/runtime/observatory/lib/src/app/location_manager.dart
+++ b/runtime/observatory/lib/src/app/location_manager.dart
@@ -34,6 +34,13 @@ class LocationManager extends Observable {
     _updateApplicationLocation(applicationPath);
   }
 
+  bool getBoolParameter(String name, bool defaultValue) {
+    var value = uri.queryParameters[name];
+    if ("true" == value) return true;
+    if ("false" == value) return false;
+    return defaultValue;
+  }
+
   /// Called whenever the browser changes the location bar (e.g. forward or
   /// back button press).
   void _onBrowserNavigation(PopStateEvent event) {